JPH10173211A - Photovoltaic element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a photovoltaic element with a high yield by increasing the light absorption of a semiconductor by using a substrate in which many polycrystalline grains having uneven surfaces and polycrystalline grains having flat surfaces are mixed due to the surface flatness of polycrystalline grains exposed on the surface of the substrate. SOLUTION: A polycrystalline substrate is formed so that polycrystalline grains having uneven surfaces and flat surfaces can be mixed in the substrate by utilizing the surface flatness difference between the polycrystalline grains exposed on the surface of the substrate. The substrate is subjected to anisotropic etching so that the etching rates of the polycrystalline grains exposed on the surface of the substrate can become different in accordance with the plane orientations of the grains. Therefore, light scattering can be reduced and the manufacturing yield of a photovoltaic element can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic device.
More specifically, the present invention relates to a photovoltaic element having improved reliability such as yield, weather resistance and durability in a manufacturing process while improving photoelectric conversion efficiency by a light confinement effect.

[0002]

2. Description of the Related Art A photovoltaic element, which is a photoelectric conversion element for converting sunlight into electric energy, is widely applied as a small power source for consumer use such as a calculator and a wristwatch. It is attracting attention as a technology that can be put to practical use as so-called fossil fuel alternative power. A photovoltaic element is a technology that uses the photovoltaic power of a pn junction of a semiconductor. A semiconductor such as silicon absorbs sunlight to generate photocarriers of electrons and holes, and the photocarriers are formed inside the pn junction. It drifts due to the electric field and is taken out.

Heretofore, the most commonly used photovoltaic elements have used single crystal silicon as a material. Such a method of manufacturing a photovoltaic element is usually performed by using a semiconductor process. Specifically, C
A single crystal of silicon whose valence is controlled to be p-type or n-type is produced by a crystal growth method such as the Z method, and the single crystal is sliced to produce a silicon wafer having a thickness of about 300 μm. Further, a pn junction is formed by forming a layer of a different conductivity type by an appropriate means such as diffusion of a valence electron controlling agent so as to have a conductivity type opposite to the conductivity type of the wafer.

[0004] By the way, such photovoltaic devices using single crystal silicon have high production costs due to the high cost of manufacturing a silicon wafer and the high cost of a manufacturing process due to the use of a semiconductor process. Therefore, the production cost per unit power generation is higher than the existing power generation method, and it is considered that it is difficult to reduce this to a level that can be used for electric power.

Therefore, in promoting the practical use of photovoltaic elements as power, it has been recognized that cost reduction and large area are important technical issues.
There has been a search for materials with high conversion efficiencies.

[0006] Materials for such a photovoltaic element include:
A tetrahedral amorphous semiconductor or polycrystalline semiconductor such as amorphous silicon, amorphous silicon germanium or amorphous silicon carbide, or II such as CdS or Cu ₂ S
-VI and III-V compound semiconductors such as GaAs and GaAlAs. In particular, a thin-film photovoltaic element using an amorphous semiconductor or a polycrystalline semiconductor for the photovoltaic generation layer can produce a film having a larger area than a photovoltaic element using single-crystal silicon. It has advantages such as being thin and being able to be deposited on an arbitrary substrate material, and is considered promising.

However, the above thin-film photovoltaic device has
The photoelectric conversion efficiency of a photovoltaic device using single-crystal silicon has not been obtained, and improvement of the photoelectric conversion efficiency and reliability have been issues to be studied for practical use as a power device. .

Accordingly, various methods have been studied as means for improving the photoelectric conversion efficiency of the thin-film photovoltaic device.

One of the important issues for improving the photoelectric conversion efficiency of a thin-film photovoltaic element is to increase light absorption in a thin-film semiconductor layer and to improve short-circuit current (Jsc). This is because if the semiconductor layer is thinned for cost reduction, light absorption is reduced as compared with a bulk semiconductor. As a technology to increase light absorption in the thin film semiconductor layer,
There are the following five techniques.

(1) Opposite to the light incident side of the photovoltaic element,
There is known a technique for forming a reflective layer using a metal film having a high reflectivity, such as Ag, Al, Cu, and Au. This technology uses light transmitted through a semiconductor layer to generate carriers,
By reflecting the light on the reflection layer, the light is absorbed again in the semiconductor layer, the light absorption in the thin film semiconductor layer is increased, the output current is increased, and the photoelectric conversion efficiency is improved.

(2) Methods of improving the surface properties of a substrate by interposing a transparent conductive layer between a back electrode and a semiconductor layer are disclosed in JP-B-59-43101 (manufactured by Fuji Electric) and JP-B-60-41878. It is disclosed in the gazette (Sharp). In these publications, the effect of interposing a transparent conductive layer between the back electrode and the semiconductor layer is to improve the flatness of the back electrode, improve the adhesion of the semiconductor layer, or alloy the metal of the back electrode with the semiconductor layer. Prevention and so on.

(3) Japanese Patent Application Laid-Open No. 60-84888 (Energy Conversion Device) discloses that a transparent conductive layer is interposed as a barrier layer between a back electrode and a semiconductor layer so that a defect region of the semiconductor layer can be removed. Techniques for reducing the flowing current have been disclosed.

(4) By interposing a transparent conductive layer of TiO ₂ between the back electrode of Ag and the semiconductor layer of amorphous silicon, the spectral sensitivity of the solar cell is improved.
Y.Hamakawa, et.al, A
ppl. Phys. Lett., 43 (1983) p644.

(5) By forming the back electrode into a concavo-convex shape (texture structure) having a size approximately equal to the wavelength of light that scatters light, long-wavelength light that cannot be completely absorbed by the semiconductor layer is scattered. T. Tiedje, et.al, Proc., A technology that extends the optical path length in the layer, improves the long wavelength sensitivity of the photovoltaic element, increases the short-circuit current, and improves the photoelectric conversion efficiency.
16th IEEE Photovoltaic Specialist Conf. (1982) p1423
And H. Deckman, et.al, Proc. 16th IEEE Photovoltai
c Specialist Conf. (1982) p1425.

By synthesizing the above techniques, a metal film having a concave-convex shape having a size approximately equal to the wavelength of light that scatters light and having a high reflectance is formed as a back surface reflection layer also serving as a back surface electrode. A configuration in which a transparent conductive layer is interposed between the back reflection layer and the semiconductor layer is considered to be most suitable.

However, when the photovoltaic element is actually manufactured by employing the back electrode having such a configuration, the following four problems are raised from the viewpoint of workability and durability.

(A) A typical uneven shape called a conventional so-called texture structure is described in T. Tiedje, et.al, Proc.
It has been considered that a material having pyramid-shaped unevenness as shown in th IEEE Photovoltaic Specialist Conf. (1982) p1423 has an excellent light confinement effect.
However, when an electrode and a semiconductor layer are formed on a substrate having such a surface shape, the leak current of the photovoltaic element increases through a defective portion of the semiconductor layer and the like, and the production yield of the photovoltaic element may decrease. there were. In addition, since the semiconductor layer formed on the surface having pyramid-shaped irregularities has a smaller effective film thickness than the semiconductor layer formed on the flat surface, the originally designed thin doping layer is further thinned. In some cases, the open-circuit voltage (Voc) and the fill factor (FF) of the photovoltaic element are lower than those of the photovoltaic element formed on the flat substrate surface.

(B) For example, when Ag or Cu is used as the back metal reflection layer, when the humidity is high and a positive bias voltage is applied to the back metal reflection layer, Ag or Cu migrates, and light incidence occurs. It turned out that the electrode on the side was conducting, and the photovoltaic element was shunted (short-circuited). This phenomenon was remarkable when the back metal reflective layer had an uneven shape (texture structure) having a size of about the wavelength of light.

(C) When Al is used as the back metal reflection layer, migration such as Ag or Cu does not occur, but when a texture structure is formed, the reflectance may decrease. Furthermore, when a transparent conductive layer is laminated on Al having a texture structure, the reflectance may be significantly reduced.

(D) When the substrate and the back surface reflection layer are formed not flat but uneven, the light scattering on the back surface is small, so that the light absorption in the semiconductor layer is not sufficient. Depending on the combination of the materials of the electrodes, the adhesion between the substrate and the backside reflective layer is insufficient, and there has been a problem that peeling may occur between the substrate and the backside reflective layer in the photovoltaic element processing step.

The above problems are caused by using low-cost substrates such as resin films and stainless steel, and increasing the production speed by increasing the formation speed of semiconductor layers. This is particularly noticeable when the process is employed, and has been a factor in lowering the production yield of the photovoltaic element.

[0022]

SUMMARY OF THE INVENTION The present invention solves the problems of workability, yield, and durability as described above by making the substrate a new structure, and further increases the light absorption of the semiconductor layer. It is another object of the present invention to provide a thin-film photovoltaic element which can be produced at a high yield, has high reliability, and has a high photoelectric conversion efficiency, at a low cost suitable for practical use.

[0023]

Means for Solving the Problems The present inventors have overcome the above-mentioned problems of processability and reliability, and have increased the light absorption of the semiconductor layer and at the same time have a photovoltaic device excellent in processability and reliability. As a result of intensive studies on a new structure and a new forming method of the substrate in order to obtain a power device, the present invention was achieved by the photovoltaic device of the present invention including the substrate having the following configuration.

That is, first, in a photovoltaic device in which a non-single-crystal semiconductor is formed on a substrate made of a polycrystalline material, a polycrystalline individual crystal grain exposed on the surface of the substrate is formed. A photovoltaic element characterized by using a substrate in which polycrystalline grains having a surface with unevenness and polycrystalline grains having a flat surface are mixed, having a difference in surface flatness.

Second, a back metal reflective layer is formed on the substrate, a transparent conductive layer is formed on the back metal reflective layer, and a non-single-crystal semiconductor is formed on the transparent conductive layer. The photovoltaic device according to claim 1, wherein:

Third, the surface of the back metal reflective layer is
The photovoltaic device according to claim 1, wherein the flatness is different depending on a polycrystalline grain boundary of the substrate.

Fourthly, the surface of the transparent conductive layer has a difference in flatness according to a polycrystalline grain boundary of the substrate. Of the photovoltaic element.

Fifthly, the surface of the photovoltaic element has a difference in flatness according to a polycrystalline grain boundary of the substrate. It is a photovoltaic element of the description.

Sixth, a step is provided on the surface of the substrate along a grain boundary of the polycrystal, or a protrusion or a depression is provided at a grain boundary portion of the polycrystal. The photovoltaic device according to any one of the above items.

Seventh, the photovoltaic device according to any one of claims 1 to 6, wherein a main material constituting the substrate is a metal or an alloy.

Eighth, the main material constituting the back metal reflection layer is a metal having high reflectance from visible to infrared light, such as gold, silver, copper, aluminum and magnesium. Item 8. The photovoltaic element according to any one of Items 1 to 7.

Ninth, the difference in flatness of the surface of each of the polycrystalline grains exposed on the surface of the substrate is 0.01 μm to 1.5 μm in the difference of Rmax. Item 9. The photovoltaic device according to any one of Items 1 to 8.

A tenth aspect is the photovoltaic device according to any one of claims 1 to 9, wherein the polycrystalline average grain size of the substrate is 0.1 μm to 2 mm. .

Eleventh, the height or depth of a step along the polycrystalline grain boundary or the height or depth of the ridge or dent at the polycrystalline grain boundary on the substrate surface is 0.0
The photovoltaic device according to claim 1, wherein the photovoltaic device has a thickness of 1 μm to 2 μm.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of each claim according to the present invention will be described below.

According to the first aspect of the present invention, in a photovoltaic device in which a non-single-crystal semiconductor is formed on a substrate made of a polycrystalline material, each of the polycrystals exposed on the surface of the substrate is provided. There is a difference in the flatness of the surface of the crystal grains, and the following effects are obtained by using a substrate in which polycrystal grains having a surface with irregularities and polycrystal grains having a flat surface are mixed.

That is, as compared with the case where a conventional polycrystalline substrate having a flat surface is used, the adhesion between the thin film laminated on the polycrystalline substrate and the polycrystalline substrate is improved, and In the power device manufacturing process, the thin film and the polycrystalline substrate are not separated from each other, so that the controllability and the degree of freedom of the manufacturing process are improved, and the manufacturing yield of the photovoltaic device is improved. In addition, as a result of accelerated weather resistance tests such as a high-temperature and high-humidity cycle test and a salt water test, weather resistance was improved. Furthermore, as a result of a mechanical strength test such as a scratch test and a bending test, the durability was improved. In addition, due to irregularities on the surface of the polycrystalline substrate, irregular reflection on the back surface of the photovoltaic element increases, and long-wavelength light that could not be absorbed by the semiconductor layer is scattered, thereby extending the optical path length in the semiconductor layer. The short-circuit current (Jsc) of the photovoltaic element increased, and the photoelectric conversion efficiency improved. Further, the series resistance of the photovoltaic element was reduced, the fill factor (FF) was improved, and the photoelectric conversion efficiency was improved. It is not clear how the series resistance is reduced, but the improved adhesion between the thin film laminated on the polycrystalline substrate and the polycrystalline substrate, and also the surface of the polycrystalline substrate When processing as in the present invention,
Since the etching is performed physically or chemically in a gas phase or a liquid phase, it is considered that impurities on the substrate surface are removed and an oxide layer on the substrate surface is removed.

Further, the leakage current of the photovoltaic element is reduced, and the production yield of the photovoltaic element is improved as compared with the case where a conventional polycrystalline substrate having a surface with unevenness is formed uniformly. did. Further, the open-circuit voltage (Voc) and the fill factor (FF) were improved while the short-circuit current (Jsc) of the photovoltaic element was maintained at a high value, and the photoelectric conversion efficiency was improved. This effect is considered as follows. That is,
The conventional so-called texture structure, as described above, has pyramid-shaped unevenness or a shape close to it, which is formed over the entire surface of the substrate, so if the unevenness is increased to enhance the light scattering effect, the pyramid peaks Although a defect portion of the semiconductor layer was likely to occur in the portion, in the case of the photovoltaic element of the present invention, the irregularities were formed in some polycrystalline grains, and the surface of the other polycrystalline grains was compared. It is considered that the defect was less likely to occur in the semiconductor layer because the target was flat. In addition, the effective thickness of a semiconductor layer stacked on a substrate having pyramid-shaped irregularities formed over the entire surface is smaller than that of a semiconductor layer stacked on a flat surface. In some cases, the open-circuit voltage (Voc) and the fill factor (FF) of the photovoltaic element are lower than those of the photovoltaic element formed on the flat substrate surface.
In the photovoltaic device of the present invention, since polycrystalline grains having irregularities and flat polycrystalline grains are mixed, the portion where the semiconductor layer is thinned is reduced, and the short-circuit current (Jsc) is high due to light scattering caused by the irregularities. It is considered that the open-circuit voltage (Voc) and the fill factor (FF) were improved while maintaining the above.

Further, when the thin film laminated on the polycrystalline substrate is also polycrystalline, the orientation of the thin film laminated on the polycrystalline substrate is improved, and the average grain size of the polycrystalline thin film is reduced. The variation in the polycrystalline grain size of the thin film was reduced. As a result, the series resistance of the photovoltaic element was reduced, and the fill factor (FF) was improved. At the same time, light scattering was further promoted, and the short-circuit current (Jsc) was increased. This effect is considered as follows. First, regarding the orientation, it is considered that the irregularities are different depending on the grain boundaries of the polycrystal of the substrate, and the plane orientations are clearly separated, so that the plane orientations of the polycrystalline thin film grown thereon are likely to be uniform. In addition, the average grain size of the polycrystals of the thin film to be laminated is such that polycrystal grains having irregularities and flat polycrystal grains are mixed, compared to a flat surface over the entire surface or a surface having pyramid-shaped irregularities over the entire surface. This is presumably because the nucleation density of the growing polycrystalline thin film was reduced and the nucleation became uniform.

According to a second aspect of the present invention, a back metal reflective layer is formed on a substrate having the features of the first aspect,
Forming a transparent conductive layer on the back metal reflective layer and forming a non-single-crystal semiconductor on the transparent conductive layer has the following effects.

That is, the reflectance of the back surface of the photovoltaic element is improved by the back metal reflective layer and the transparent conductive layer, and the irregular reflection is improved by the polycrystalline substrate having the features of claim 1. Due to the synergistic effect, the optical path length in the semiconductor layer was increased, the light absorption was increased, the short-circuit current (Jsc) of the photovoltaic element was further increased, and the photoelectric conversion efficiency was further improved. In addition, by improving the adhesion between the back metal reflective layer and the polycrystalline substrate, the degree of freedom and controllability of the manufacturing process of the photovoltaic element is improved, and the production yield is improved, and the photovoltaic element is improved. The weather resistance and durability have improved. In addition, since the transparent conductive layer has an appropriate resistance value, the current flowing in the defect region of the semiconductor layer is reduced, and the shunt of the photovoltaic element is reduced, and the production yield is improved. Further, the polycrystalline substrate may be a polycrystalline substrate.
With this feature, the orientation of the back metal reflective layer and the transparent conductive layer is improved, the average grain size of the polycrystal of the back metal reflective layer is increased, and the variation in the grain size is reduced. As a result, the series resistance of the photovoltaic element was reduced, and the fill factor (FF) was improved. At the same time, light scattering was further promoted, and the short-circuit current (Jsc) was increased.

According to the third aspect of the present invention, the surface of the back metal reflection layer has a difference in flatness according to the polycrystalline grain boundaries of the substrate, and thus has the following effects. .

That is, by improving the adhesion between the back metal reflective layer and the transparent conductive layer, the degree of freedom and controllability of the manufacturing process of the photovoltaic element are further improved, the production yield is further improved, and the photovoltaic element is improved. The weather resistance and durability of the power element were further improved. In addition, the surface of the back metal reflective layer also has a difference in flatness according to the polycrystalline grain boundaries of the substrate, so that the orientation of the transparent conductive layer is further improved, and the average grain size of the polycrystalline transparent conductive layer is reduced. And the variation in particle size became smaller. As a result, the series resistance of the photovoltaic element decreases, the fill factor (FF) improves, and at the same time, light scattering at the interface between the back metal reflective layer and the transparent conductive layer and the interface between the transparent conductive layer and the semiconductor layer further increases. Accelerated, the short circuit current (Jsc) further increased.

According to the fourth aspect of the invention, the surface of the transparent conductive layer has a difference in flatness according to a polycrystalline grain boundary of the substrate, and thus has the following effects.

That is, since the adhesion between the transparent conductive layer and the semiconductor layer is improved, the degree of freedom and controllability of the manufacturing process of the photovoltaic element are further improved, and the production yield is further improved. The weather resistance and durability were further improved. The surface of the transparent conductive layer also has a difference in flatness according to the polycrystalline grain boundaries of the substrate, so that light scattering at the interface between the transparent conductive layer and the semiconductor layer is promoted, and the short-circuit current (Js
c) further increased.

According to the fifth aspect of the present invention, since the surface of the photovoltaic element has a difference in flatness according to the polycrystalline grain boundary of the substrate, the light incident on the photovoltaic element can be improved. Light scattering is promoted at the side, especially at the interface between the semiconductor layer and the upper transparent electrode, and light is scattered on both the light incident side and the back side of the semiconductor layer, and the optical path length in the semiconductor layer is reduced. Extending further, light absorption increased and short circuit current (Jsc) further increased.

Further, according to the invention of claim 6, by providing a step along the polycrystalline grain boundary on the surface of the substrate or by providing a protrusion or a dent at the polycrystalline grain boundary portion, The adhesion between the thin film laminated on the crystalline substrate and the polycrystalline substrate is further improved, the degree of freedom and controllability of the photovoltaic element manufacturing process is further improved, and the production yield is further improved, The weather resistance and durability of the photovoltaic element were further improved. In addition, due to steps or irregularities in the crystal grain boundaries on the surface of the polycrystalline substrate, irregular reflection on the back surface of the photovoltaic element increases, and long-wavelength light that could not be absorbed by the semiconductor layer is scattered into the semiconductor layer. , The short-circuit current (Jsc) of the photovoltaic element further increased, and the photoelectric conversion efficiency was further improved. Further, the orientation of the polycrystalline thin film laminated on the polycrystalline substrate was further improved, and the average grain size of the polycrystalline thin film was further increased. As a result, the series resistance of the photovoltaic element decreases, and the fill factor (F
At the same time as F) was improved, light scattering was further promoted and the short-circuit current (Jsc) was increased.

According to the seventh aspect of the present invention, since the main material constituting the substrate is a metal or an alloy, a difference in flatness is provided according to a polycrystalline grain boundary. It is easy to form steps along the boundaries or irregularities at the grain boundaries of polycrystals. In addition, flexibility is generated in the substrate, and the degree of freedom in processing in manufacturing the photovoltaic element is improved. In addition, since both the polycrystalline substrate and the back metal reflective layer are made of metal, the adhesion between the polycrystalline substrate and the back metal reflective layer is further improved, and the orientation of the back metal reflective layer is further improved. . Due to the improved adhesion, the processability of the substrate is further improved, and the flexibility and controllability of the manufacturing process are further improved.

According to the eighth aspect of the invention, the main material constituting the back metal reflection layer is a metal having a high reflectance from visible to infrared light, such as gold, silver, copper, aluminum, and magnesium. This has the following effects.

That is, the reflectance of the back surface of the photovoltaic element was further improved, the light absorption of the semiconductor layer was increased, and the short-circuit current (Jsc) of the photovoltaic element was further improved.

When the above-mentioned metal having a high reflectivity is laminated on the surface of a substrate on which a so-called texture structure having pyramid-shaped irregularities is formed on the entire surface, or the back surface made of the metal having a high reflectivity is used Metal reflective layer,
In the case where the conventional pyramid-shaped uneven texture structure is provided over the entire surface, the above-mentioned metal having a high reflectance is likely to diffuse into the semiconductor layer or cause migration, thereby causing a shunt of the photovoltaic element. in the case of,
There is a difference in the flatness of the surface of the individual crystal grains of the polycrystal exposed on the surface of the polycrystalline substrate, and polycrystals in which polycrystal grains having irregularities formed on the surface and polycrystal grains having a flat surface are mixed. By laminating the above-mentioned high-reflectivity metal on the substrate, the high-reflectivity metal diffuses into the semiconductor layer or migrates while maintaining high diffuse reflection and high short-circuit current (Jsc). Is almost eliminated, and the production yield of the photovoltaic element is remarkably improved.
Further, the leak current of the photovoltaic element was reduced, and the open voltage (Voc) and the fill factor (FF) were improved.

Further, it is most desirable to use aluminum as the main material of the back metal reflection layer, because the production cost is low and migration is less likely to occur as compared with silver or copper. If aluminum is laminated on the surface of the substrate on which a so-called texture structure having irregularities is formed over the entire surface, or if aluminum has a conventional pyramid-shaped irregular texture structure over the entire surface of the substrate, the total reflectance of the aluminum surface Often decreased.
In addition, when a transparent conductive layer is laminated on the above-described aluminum, the total reflectance often lowers in many cases, and is often unsuitable as a back reflection layer of a photovoltaic element. On the other hand, when aluminum is stacked on a flat substrate, the scattering of light on the back surface of the semiconductor layer is reduced and the short-circuit current (Jsc) of the photovoltaic element is reduced. There was a problem that separation easily occurred between the two. On the other hand, according to the present invention, there is a difference in the flatness of the surface of each of the polycrystalline grains exposed on the surface of the polycrystalline substrate. By laminating aluminum on a polycrystalline substrate in which crystal grains are mixed, light is scattered on the back surface, and the total reflectance of the aluminum surface including the case where a transparent conductive layer is laminated is reduced. The light absorption of the semiconductor layer was improved by the high total reflectance of the aluminum surface, and the short-circuit current (Jsc) of the photovoltaic element was improved. In addition, the adhesion between the substrate and aluminum was improved, the flexibility and controllability of the manufacturing process were improved, the manufacturing yield was improved, and the weather resistance and durability of the photovoltaic element were improved.

The reason why the total reflectance of the aluminum surface having a pyramid-shaped irregular texture structure over the entire surface is lowered is not clear, but the minute pyramid-shaped irregularities on the order of the wavelength of light cause the aluminum to have a low reflectance. It is considered that the surface area increases, a reaction easily occurs at the interface with the transparent conductive layer, and a compound is formed at the interface, thereby lowering the reflectance. In the configuration of the present invention, there is a difference in the flatness of the surfaces of the individual crystal grains of the polycrystal exposed on the substrate surface, and polycrystal grains having irregularities formed on the surface and polycrystal grains having a flat surface are mixed. It is considered that the increase in the surface area of aluminum was suppressed, the reaction at the interface with the transparent conductive layer was suppressed, and the total reflectance was significantly improved.

Hereinafter, embodiments of the present invention will be described.

(Photovoltaic Element) The photovoltaic element according to the present invention includes, for example, those shown in FIGS. Hereinafter, the configuration of the photovoltaic element of the present invention and the method of manufacturing the same will be described in more detail with reference to the drawings.

FIG. 1 is an example of a sectional view of a photovoltaic device for explaining the concept of the present invention in detail. However, the present invention is not limited to the photovoltaic element having the configuration shown in FIG. In FIG. 1, 101 is a substrate, 102 is a back metal reflective layer, 103 is a transparent conductive layer, 104 is an n-type semiconductor layer, 1
05 is an i-type semiconductor layer, 106 is a p-type semiconductor layer, 107 is a transparent electrode, and 108 is a current collecting electrode. FIG. 1 shows a configuration in which light enters from the p-type semiconductor layer side. In the case of a photovoltaic element having a configuration in which light enters from the n-type semiconductor layer side,
Is a p-type semiconductor layer, and 106 is an n-type semiconductor layer.

FIG. 1 shows a configuration in which light is incident from the side opposite to the substrate. In a photovoltaic element having a configuration in which light is incident from the substrate side, the layers are arranged in the reverse order to FIG. 1 except for the substrate. May be laminated.

FIG. 2 is an example of a sectional view of a stack type photovoltaic device for explaining the concept of the present invention in detail. The stack type photovoltaic device of the present invention shown in FIG.
215 is a first pin junction counted from the light incident side, 216 is a second pin junction, and 217 is a third pin junction. These three pin junctions are formed on the substrate 201 on the backside metal reflection layer 2.
02 and a transparent conductive layer 203 are formed and laminated thereon. The transparent electrode 2 is formed on the top of the three pin junctions.
13 and the collecting electrode 214 are formed to form a stacked photovoltaic element. The respective pin junctions are formed by n-type semiconductor layers 204, 207, 210, i-type semiconductor layers 205, 208, 211, p-type semiconductor layers 206,
09, 212. Further, as in the photovoltaic element of FIG. 1, the arrangement of the doping layers and the electrodes may be switched depending on the incident direction of light.

Hereinafter, the respective layers of the photovoltaic element of the present invention will be described in detail in the order in which they are formed.

(Substrate) The substrate according to the present invention is a feature of the present invention, and is particularly characterized by its crystal form and surface shape.

As the crystal form, a polycrystalline one is used.

As a result of the study, the present inventor has found that the surface shape of the polycrystalline substrate has a difference in the flatness of the surface of each of the polycrystalline grains exposed on the surface of the substrate, and the formation of irregularities It has been found that a shape in which polycrystalline grains having a given surface and polycrystalline grains having a flat surface are mixed is preferable.

Further, if the difference in flatness of the surface of each of the polycrystalline grains exposed on the surface of the substrate is too small,
That is, it means that the substrate is flat over the entire surface or has a textured structure over the entire surface. In either case, conventional problems such as a decrease in light scattering or an increase in leakage current of the photovoltaic element appear. It turned out to be. Also, if the difference in flatness of the surface of individual crystal grains of the polycrystal exposed on the surface of the substrate is too large, there are polycrystal grains having large irregularities on the surface, so that a conventional texture structure is formed. As in the case of the substrate, the shunt or leakage current of the photovoltaic element is increased, or the open circuit voltage (Voc) or the fill factor (F
It was found that problems such as a decrease in F) appeared.

Therefore, the difference in the flatness of the surface of the individual crystal grains of the polycrystal exposed on the surface of the substrate is the difference of Rmax,
Preferably from 0.01 μm to 1.5 μm, more preferably from 0.02 μm to 1 μm, optimally 0.05 μm
It has been found that m to 0.7 μm is desirable.

On the other hand, if the average grain size of the polycrystal is too small (less than 0.05 μm), it tends to be either flat over the entire surface of the substrate or a textured structure over the entire surface. In this case as well, conventional problems such as a decrease in light scattering, an increase in leak current of the photovoltaic element, and a decrease in shunt or open-circuit voltage (Voc) or fill factor (FF) of the photovoltaic element appear. I understood. Further, it was found that when the average grain size of the polycrystalline grains was too large (exceeding 2 mm), irregular reflection on the back surface of the photovoltaic element was reduced, and the short-circuit current (Jsc) was reduced.

Therefore, the average particle size of the polycrystal is preferably 0.1 μm to 2 mm, more preferably 0.2 μm to 2 mm.
μm to 1 mm, optimally 0.5 μm to 100 μm
Is desirable.

Further, in a photovoltaic element in which a step is formed along the polycrystalline grain boundary on the surface of the substrate, or a bump or a dent is formed in the polycrystalline grain boundary, the polycrystalline grain boundary is formed. If the height of the step or unevenness along the surface is too small, the scattering of light is reduced and the short-circuit current (Js) of the photovoltaic element is reduced.
It was found that when c) was reduced, and when it was too large, the leakage current of the photovoltaic element increased and the production yield was sometimes reduced.

Therefore, steps along the polycrystalline grain boundaries,
Alternatively, the height or depth of the ridge or dent at the grain boundary portion of the polycrystal is preferably 0.01 μm to 2 μm.
m, more preferably from 0.02 μm to 1.5 μm, optimally from 0.03 μm to 1 μm. In addition, it is preferable that the flatness of the surface of each of the polycrystalline grains exposed on the surface of the substrate is smaller than the height of the steps or the irregularities along the polycrystalline grain boundaries. If the Rmax of the surface in each crystal grain is large, it approaches a conventional so-called texture structure, so that the leak current increases and the shunt or open circuit voltage (Voc) or fill factor (FF) of the photovoltaic element decreases. The problem of the conventional texture structure comes out. Therefore, the flatness of the surface within each crystal grain depends on the height of steps or irregularities along the polycrystalline grain boundaries.
Although the suitable range is different, preferably, Rmax is 2 μm or less, more preferably, Rmax is 1.5 μm or less, and most preferably, Rmax is 1 μm or less.

The material of the substrate may be a conductive material or an electrically insulating material. Further, they may be light-transmitting or non-light-transmitting, but preferably have a small amount of deformation and distortion and a desired strength. Specifically, Fe, Ni, Cr, Al, Mo, Au, Nb, Ta,
Metals such as V, Ti, Pt, Pb or alloys thereof, for example, polycrystalline materials of thin plates such as brass and stainless steel and composites thereof, or SiO ₂ , Si ₃ N ₄ , Al ₂ O ₃ , A
An insulating polycrystalline material containing 1N or the like can be used. When the substrate is electrically conductive such as a metal, the substrate may be directly used as an electrode for extracting current. When the substrate is insulative, the back metal reflective layer described later also serves as a back electrode, or when the substrate is translucent, a transparent electrode described later is formed on the substrate. An electrode for direct current extraction. Of course, even if the substrate is an electrically conductive material such as a metal, the reflectance of long-wavelength light on the substrate surface is improved, and the mutual diffusion of constituent elements between the substrate material and the deposited film is prevented. A different kind of metal layer or the like may be provided on the side of the substrate on which the deposited film is formed, for the purpose of, for example, performing a process.

The shape of the substrate can be plate-like, long belt-like, cylindrical, or the like depending on the application. The thickness of the substrate is appropriately determined so that a desired photovoltaic element can be formed. When flexibility is required as a photovoltaic element,
The thickness can be made as thin as possible within a range where the function as a substrate is sufficiently exhibited. However, from the viewpoint of the production and handling of the substrate, the mechanical strength, etc., usually 10 μm
That is all.

(Method of Surface Treatment of Substrate) The method of forming a polycrystalline substrate having the features of the present invention described above differs depending on the material of the substrate, but the following method of surface treatment of the substrate can be employed. .

That is, there is a difference in the flatness of the surface of each of the polycrystalline grains exposed on the surface of the polycrystalline substrate, and the polycrystalline grains having irregularities on the surface and the polycrystalline grains having a flat surface are different. In order to make them coexist, by performing anisotropic etching in which the etching rate varies depending on the plane orientation of the polycrystal exposed on the substrate surface, physically or chemically, in the gas phase or liquid phase, can get.

More specifically, when the etching is performed in a gas phase, gas etching, plasma etching, ion etching, or the like can be used. As the etching gas, CF ₄ ,
C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₁₀ , CHF ₃ , CH ₂ F ₂ , C
l ₂ , ClF ₃ , CCl ₄ , CCl ₂ F ₂ , CCIF ₃ , CH
ClF ₂ , C ₂ Cl ₂ F ₄ , BCl ₃ , PCl ₃ , CBr
F ₃ , SF ₆ , SiF ₄ , SiCl ₄ , HF, O ₂ , N ₂ , H
₂ , He, Ne, Ar, Xe and the like or a mixed gas thereof. The gas pressure in the case of plasma etching is 10 ⁻³ Torr to 1 Torr, and DC or AC or 1
A high frequency such as an RF wave of 100 MHz or a microwave of 0.1 to 10 GHz can be used.

When the reaction is carried out in a liquid phase, examples of the acid include
Sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, hydrofluoric acid, chromic acid, sulfamic acid, oxalic acid, tartaric acid, citric acid, formic acid, lactic acid,
Glycolic acid, acetic acid, gluconic acid, succinic acid, malic acid, etc., or those diluted with water, or a mixture thereof can be used. Examples of the alkali include sodium hydroxide, ammonium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, sodium sesquicarbonate, sodium primary phosphate, sodium secondary phosphate, sodium tertiary phosphate, sodium pyrophosphate, and sodium tripolyphosphate. Sodium acid, sodium tetrapolyphosphate, sodium trimetaphosphate, sodium tetrametaphosphate, sodium hexametaphosphate, sodium orthosilicate, sodium metasilicate, etc., or those diluted with water, or a mixture thereof can be used. it can. When etching is performed in a liquid phase, the etching liquid may be heated or energy such as ultrasonic waves may be applied.

Further, preferable etching conditions greatly differ depending on the polycrystalline material or surface shape.
Although it cannot be specified unconditionally, as an example, in the case of a ferrite stainless steel SUS430-BA having a thickness of 0.2 mm and subjected to a bright annealing treatment, the following conditions are preferable.

For example, when etching is performed in a gas phase, 47
Ar was set to 10 with SUS430-BA cut into a square of 10 mm set in a substrate holder of a sputtering apparatus.
１５０150 sccm, gas pressure 2-30 mTorr
r, and 13.5 of 100 W to 400 W is applied to the substrate side.
It is desirable to apply a 6 MHz RF high frequency to generate Ar plasma and etch the substrate surface by Ar plasma treatment for 5 to 30 minutes. Of course, other etching gas may be used, and plasma may be generated by other energy such as DC power or microwave. In that case, naturally, suitable conditions differ depending on the gas and energy.

When the above-described SUS430-BA is etched in a liquid phase, for example, an etching solution in which hydrofluoric acid, nitric acid and water are mixed at a ratio of 1: 3: 200 is used for one minute while stirring. It is desirable to perform etching for up to 20 minutes. Of course, other etching liquids such as a mixed liquid of hydrofluoric acid, nitric acid, acetic acid and water or a mixed liquid of hydrochloric acid, nitric acid and water can be used. The preferred etching time varies depending on the type of etching solution or the mixing ratio. In the case of an acid or alkali having a strong etching effect on a certain substrate material, it is desirable to increase the dilution ratio and to shorten the etching time.

In both the gas phase etching and the liquid phase etching, stronger etching conditions are preferable as the surface state of the substrate is closer to the mirror surface. For example, the same SU
In step S430, the mirror-polished surface preferably has etching conditions stronger than those described above. Also,
When the same stainless steel has a slightly different composition such as a martensitic stainless steel or an austenitic stainless steel, the suitable etching conditions are different. For example, in the case of SUS304 of austenitic stainless steel, S
Etching conditions stronger than US430 are preferred. In the case of liquid phase etching, SUS4
Even in the case of 30-BA, when the thickness of the substrate is larger than the above-described value, the etching condition that is stronger than the above-described etching condition is preferable.

(Back Metal Reflective Layer) The back metal reflective layers 102 and 202 according to the present invention are arranged on the back surface of the semiconductor layer in the light incident direction, and reflect light that could not be absorbed by the semiconductor layer again to the semiconductor layer. It has the role of a light reflecting layer. In addition, it also serves as the back electrode of the photovoltaic element. Therefore, 10 in FIG.
When the substrate 101 is translucent and light enters from the direction of the substrate, the substrate is laminated on the semiconductor layer with the transparent conductive layer interposed therebetween. Materials for the back metal reflective layer include gold, silver, copper, aluminum, magnesium, nickel, iron, chromium, molybdenum, tungsten, titanium,
Examples include metals such as cobalt, tantalum, niobium, and zirconium, and alloys such as stainless steel. Among them, metals having high reflectivity such as aluminum, magnesium, copper, silver, and gold are particularly preferable. By using a metal having a high reflectance, light that could not be absorbed by the semiconductor layer is reflected again by the semiconductor layer with a high reflectance, an optical path length in the semiconductor layer is increased, and light absorption of the semiconductor layer is increased. The short-circuit current (Jsc) of the photovoltaic element increases.

The surface of the back metal reflective layer may be flat, but the difference in flatness according to the polycrystalline grain boundaries of the substrate improves the adhesion between the back metal reflective layer and the transparent conductive layer. However, the flexibility and controllability of the manufacturing process of the photovoltaic element were further improved, the production yield was further improved, and the weather resistance and durability of the photovoltaic element were further improved. In addition, the surface of the back metal reflective layer also has a difference in flatness according to the polycrystalline grain boundaries of the substrate, so that the orientation of the transparent conductive layer is further improved, and the average grain size of the polycrystalline transparent conductive layer is reduced. And the variation in particle size became smaller. As a result, the series resistance of the photovoltaic element is reduced, and the fill factor (FF) is improved. At the same time, light scattering at the interface between the back metal reflective layer and the transparent conductive layer is further promoted, and the short-circuit current (Jsc) is reduced. Increased further.

The difference in flatness of the back metal reflecting layer according to the polycrystalline grain boundaries is the difference in Rmax, preferably 0.01 μm.
To 1.5 μm, more preferably 0.02 μm to 1
μm, and most preferably, 0.05 μm to 0.7 μm.

If the Rmax of the surface in each crystal grain is large, it approaches the conventional so-called texture structure, so that the leakage current increases, the shunt or open-circuit voltage (Voc) or the fill factor (Voc) of the photovoltaic element increases. The problem of the conventional texture structure such as a decrease in FF) appears. Therefore, the flatness of the surface of the back metal reflective layer in each crystal grain is preferably 2 μm or less in Rmax, more preferably 1.5 μm or less in Rmax, and most preferably 1 μm or less in Rmax.

When the thickness of the back metal reflective layer is reduced to, for example, 0.1 μm or less, the surface of the back metal reflective layer inherits the surface properties of the polycrystalline substrate of the present invention and forms a polycrystalline grain boundary. Steps or irregularities along the surface appear. When the thickness of the back metal reflection layer is increased to, for example, 1 μm or more, the surface becomes flat.

Further, similarly to the case where the surface of the back metal reflection layer is formed on a polycrystalline substrate, steps or irregularities may be formed along the polycrystalline grain boundaries by etching.

For the formation of the back metal reflection layer, various vapor deposition methods such as EB vapor deposition and sputter vapor deposition, various CVD methods, plating methods, printing methods and the like are used.

(Transparent conductive layer) The transparent conductive layer 1 according to the present invention
03 is a back metal reflection layer 10 mainly for the following purposes.
2 and the semiconductor layer 104. First, the irregular reflection on the back surface of the photovoltaic element is improved, light is confined in the photovoltaic element by multiple interference by the thin film, the optical path length in the semiconductor layer is extended, and the short-circuit current (Jsc) of the photovoltaic element is increased. To increase. Next, it is necessary to prevent the metal of the back metal reflective layer also serving as the back electrode from diffusing into the semiconductor layer or causing migration, thereby preventing the photovoltaic element from shunting. In addition, by giving the transparent conductive layer a slight resistance value, short-circuiting caused by defects such as pinholes in the semiconductor layer between the back metal reflection layer 102 and the transparent electrode 107 provided with the semiconductor layer interposed therebetween is prevented. It is to be.

The transparent conductive layer 103 is required to have a high transmittance in a wavelength region that can be absorbed by the semiconductor layer and to have an appropriate resistivity. Preferably, the transmittance at 650 nm or more is 80% or more, more preferably 85% or more, and optimally 90% or more. Further, the resistivity is preferably 1 × 10 ⁻⁴ Ωcm or more and 1 × 10 ⁶ Ωcm.
Or less, more preferably 1 × 10 ⁻² Ωcm or more, and 5 × 1
0 is desirably ⁴ [Omega] cm or less.

The material of the transparent conductive layer 103 is In ₂
O ₃ , SnO ₂ , ITO (In ₂ O ₃ + SnO ₂ ), Zn
O, CdO, Cd ₂ SnO ₄ , TiO ₂ , Ta ₂ O ₅ , Bi ₂
A conductive oxide such as O ₃ , MoO ₃ , and Na _x WO ₃ or a mixture thereof is preferably used. Further, an element (dopant) that changes the conductivity may be added to these compounds.

As an element (dopant) for changing the conductivity, for example, when the transparent conductive layer 103 is ZnO,
Al, In, B, Ga, Si, F, etc., In the case of In ₂ O ₃ , Sn, F, Te, Ti, Sb, Pb, etc., and in the case of SnO ₂ , F, Sb, P, As, In, T
1, Te, W, Cl, Br, I, etc. are preferably used.

The transparent conductive layer 103 may be formed by various deposition methods such as EB deposition and sputter deposition, and various C methods.
A VD method, a spray method, a spin-on method, a dipping method and the like are preferably used.

The surface of the transparent conductive layer 103 may be flat, but due to the difference in flatness depending on the polycrystalline grain boundaries of the substrate, the adhesion between the transparent conductive layer and the semiconductor layer is improved, The flexibility and controllability of the manufacturing process of the photovoltaic device were further improved, the production yield was further improved, and the weather resistance and durability of the photovoltaic device were further improved. In addition, light scattering at the interface between the transparent conductive layer and the semiconductor layer was promoted, and the short-circuit current (Jsc) was further increased. The difference in flatness of the transparent conductive layer 103 according to the polycrystalline grain boundaries is preferably 0.01 μm.
m to 1.5 μm, more preferably 0.02 μm to 1 μm, and most preferably 0.05 μm to 0.7 μm.

Further, due to the polycrystalline growth of the transparent conductive layer, irregularities may be formed on the surface according to the growth surface. In addition, since the polycrystalline substrate has a difference in flatness according to the polycrystalline grain boundaries of the substrate, the average crystal grain size of the polycrystal of the transparent conductive layer is increased, and light scattering is increased. The short-circuit current (Jsc) of the electromotive element further improved.

(Semiconductor Layer) As a material of the semiconductor layer according to the present invention, a material using a group IV element such as Si, C, Ge, or the like, a material using a group IV alloy such as SiGe, SiC, SiSn, or II- such as CdS and CdTe
Using a group VI element, or CuInSe ₂ , C
I-III-V such as u (InGa) Se ₂ , CuInS ₂
Those using Group I elements are used.

Among the above semiconductor materials, semiconductor materials particularly preferably used for the photovoltaic device of the present invention include a-Si: H (abbreviation for hydrogenated amorphous silicon), a
-Si: F, a-Si: H: F, a-SiGe: H, a
-SiGe: F, a-SiGe: H: F, a-SiC:
Group IV and group IV alloy-based amorphous semiconductor materials such as H, a-SiC: F and a-SiC: H: F, microcrystalline semiconductor materials, and polycrystalline semiconductor materials are given.

The semiconductor layer can perform valence electron control and forbidden band width control. Specifically, a raw material compound containing an element serving as a valence electron controlling agent or a forbidden band width controlling agent when forming a semiconductor layer is used alone, or mixed with the deposited film forming raw material gas or the diluent gas to form a film. You only have to introduce it in the space.

The semiconductor layer can be controlled by valence electrons.
At least a portion is doped p-type and n-type to form at least one set of pin junctions. And
By stacking a plurality of pin junctions, a so-called stack cell configuration is obtained.

As a method for forming a semiconductor layer, microwave plasma CVD, RF plasma CVD, light C
VD method, thermal CVD method, various CVD methods such as MOCVD method, or various evaporation methods such as EB evaporation, MBE, ion plating, ion beam method, sputtering method,
It is formed by a spray method, a printing method, or the like. As a method adopted industrially, a plasma CVD method in which a raw material gas is decomposed by plasma and deposited on a substrate is preferably used. In addition, as the reaction device, a batch type device, a continuous film forming device, or the like can be used as desired.

Hereinafter, a semiconductor layer using a group IV and group IV alloy amorphous semiconductor material particularly suitable for the photovoltaic device of the present invention will be described in more detail.

(1) i-type semiconductor layer (intrinsic semiconductor layer) Particularly in a photovoltaic device using a group IV or group IV alloy-based amorphous semiconductor material, the i-type layer used for the pin junction is exposed to irradiation light. It is an important layer for generating and transporting carriers.

As the i-type layer, a slightly p-type or slightly n-type layer can be used.

As described above, the group IV and group IV alloy non-single-crystal semiconductor materials contain a hydrogen atom (H, D) or a halogen atom (X), which has an important function.

The hydrogen atoms (H, D) or the halogen atoms (X) contained in the i-type layer work to compensate for dangling bonds in the i-type layer, and the carrier in the i-type layer is To improve the product of the mobility and the lifetime. Also p
It has a function of compensating the interface state of each interface of the mold layer / i-type layer and the n-type layer / i-type layer, and has an effect of improving the photovoltaic power, the photocurrent, and the photoresponsiveness of the photovoltaic element. It is. The number of hydrogen atoms and / or halogen atoms contained in the i-type layer is 1 to
40 atm% is mentioned as the optimum content. Especially,
A preferred distribution form is one in which a large content of hydrogen atoms and / or halogen atoms is distributed on each interface side of the p-type layer / i-type layer and the n-type layer / i-type layer. The preferred range of the content of hydrogen atoms and / or halogen atoms is 1.1 to 2 times the content in the bulk. Further, it is preferable that the content of hydrogen atoms and / or halogen atoms is changed in accordance with the content of silicon atoms.

In the stack type photovoltaic element, the material of the pin-junction i-type semiconductor layer near the light incident side includes a material having a wide band gap and a p-type material far from the light incident side.
As a material for the in-junction i-type semiconductor layer, a material having a narrow band gap is preferably used.

Amorphous silicon and amorphous silicon germanium are formed by an element for compensating for a dangling bond.
a-Si: H, a-Si: F, a-Si: H: F, a-
SiGe: H, a-SiGe: F, a-SiGe: H:
It is written as F or the like.

Further, the characteristics of the i-type semiconductor layer suitable for the photovoltaic device of the present invention include a hydrogen atom content (C
H): 1.0-25.0%, AM1.5, 100 mW
/ Cm ² photoelectric conductivity (σp) under simulated sunlight irradiation,
1.0 × 10 ⁻⁷ S / cm or more, dark conductivity (σd)
1.0 × 10 ⁻⁹ S / cm or less, Urbach Energy by Constant Photocurrent Method (CPM)
Those having a local state density of 10 ¹⁷ / cm ³ or less are preferably used.

(2) P-type semiconductor layer or n-type semiconductor layer As the amorphous material (denoted as a-) or the microcrystalline material (denoted as μc-) of the p-type semiconductor layer or the n-type semiconductor layer, For example, a-Si: H, a-Si: HX, a-S
iC: H, a-SiC: HX, a-SiGe: H, a-
SiGe: HX, a-SiGeC: H, a-SiGe
C: HX, a-SiO: H, a-SiO: HX, a-S
iN: H, a-SiN: HX, a-SiON: H, a-
SiON: HX, a-SiOCN: H, a-SiOC
N: HX, μc-Si: H, μc-Si: HX, μc −
SiC: H, μc-SiC: HX, μc-SiO: H,
μc-SiO: HX, μc-SiN: H, μc-Si
N: HX, μc-SiGeC: H, μc-SiGeC:
HX, μc-SiON: H, μc-SiON: HX, μ
c-SiOCN: H, μc-SiOCN: HX, etc., p-type valence electron controlling agents (Group III atoms B, Al, G
a, In, Tl) and n-type valence electron controlling agents (Periodic Table No. V
Examples of the polycrystalline material (denoted as poly-) include poly-Si: H and poly-Si: H.
X, poly-SiC: H, poly-SiC: HX,
poly-SiO: H, poly-SiO: HX, po
ly-SiN: H, poly-SiN: HX, poly
-SiGeC: H, poly-SiGeC: HX, po
ly-SiON: H, poly-SiON: HX, po
ly-SiOCN: H, poly-SiOCN: HX,
poly-Si, poly-SiC, poly-Si
O, poly-SiN, etc., p-type valence electron control agents (Group III atoms B, Al, Ga, In, Tl in the periodic table) and n-type valence electron control agents (Group V atoms P, P in the periodic table) As, Sb,
A material to which Bi) is added at a high concentration is exemplified.

In particular, the p-type layer or the n-type layer on the light incident side includes:
A crystalline semiconductor layer with little light absorption or an amorphous semiconductor layer with a wide band gap is suitable.

The addition amount of Group III atoms of the periodic table to the p-type layer and the addition amount of Group V atoms of the periodic table to the n-type layer are 0.
The optimal amount is 1 to 50 atm%.

Further, hydrogen atoms (H, D) or halogen atoms contained in the p-type layer or the n-type layer work to compensate for dangling bonds of the p-type layer or the n-type layer, and To improve the doping efficiency. The number of hydrogen atoms or halogen atoms added to the p-type layer or the n-type layer is 0.
The optimal amount is 1 to 40 atm%. In particular, when the p-type layer or the n-type layer is crystalline, the optimum amount of hydrogen atoms or halogen atoms is 0.1 to 8 atm%. Further, a preferred distribution form is one in which a large content of hydrogen atoms and / or halogen atoms is distributed on each interface side of the p-type layer / i-type layer and the n-type layer / i-type layer. The content of the hydrogen atom and / or the halogen atom is preferably in a range of 1.1 to 2 times the content in the bulk. By increasing the content of hydrogen atoms or halogen atoms in the vicinity of each interface between the p-type layer / i-type layer and the n-type layer / i-type layer, the defect level and mechanical strain near the interface are reduced. Accordingly, the photovoltaic power and the photocurrent of the photovoltaic device of the present invention can be increased.

The electrical characteristics of the p-type layer and the n-type layer of the photovoltaic element are preferably those having an activation energy of 0.2 eV or less, and those having an activation energy of 0.1 eV or less are optimal. The non-resistance is preferably 100 Ωcm or less, and most preferably 1 Ωcm or less. Further, the layer thickness of the p-type layer and the n-type layer is 1 to
50 nm is preferred, and 3 to 10 nm is optimal.

Examples of a p-type semiconductor layer or an n-type semiconductor layer using II-VI group elements include CdS and CdT.
e, ZnO, ZnSe, etc., and I-III-VI
Examples of using Group ₂ elements include CuInSe ₂ , Cu (I
nGa) Se ₂ , CuInS ₂ , CuIn (Se,
S) ₂ , CuInGaSeTe and the like.

(3) Method of Forming Semiconductor Layer In order to form a suitable group IV and group IV alloy amorphous semiconductor layer as a semiconductor layer of the photovoltaic device of the present invention, a preferable manufacturing method is RF This is a plasma CVD method using an alternating current or a high frequency such as a plasma CVD method or a microwave plasma CVD method.

In the microwave plasma CVD method, a material gas such as a raw material gas or a diluent gas is introduced into a deposition chamber (vacuum chamber) which can be decompressed, and the inside pressure of the deposition chamber is kept constant while being evacuated by a vacuum pump. The microwave oscillated by the microwave power supply is guided by a waveguide, introduced into the deposition chamber through a dielectric window (alumina ceramics or the like), and generated by decomposing a material gas plasma,
This is a method for forming a desired deposited film on a substrate placed in a deposition chamber, and can form a deposited film applicable to a photovoltaic device under a wide range of deposition conditions.

When the semiconductor layer for a photovoltaic device of the present invention is deposited by microwave plasma CVD, the substrate temperature in the deposition chamber is 100 to 450 ° C., and the internal pressure is 0.5 to 30 m.
Torr, microwave power is 0.01 to 1 W / c
m ³ and the frequency of the microwave are preferably in the range of 0.1 to 10 GHz.

When the deposition is performed by the RF plasma CVD method, the substrate temperature in the deposition chamber is 100 to 350 ° C., the internal pressure is 0.1 to 10 Torr, and the RF power is 0.001.
５5.0 W / cm ³ , the deposition rate is 0.1-30 Å / s
ec is a preferred condition.

The source gas suitable for depositing the group IV and group IV alloy-based amorphous semiconductor layer suitable for the photovoltaic device of the present invention includes a gasizable compound containing silicon atoms,
Examples include a gasizable compound containing a germanium atom, a gasizable compound containing a carbon atom, and a mixed gas of the compound.

As a gaseous compound containing a silicon atom, a chain or cyclic silane compound is used. Specifically, for example, SiH ₄ , Si ₂ H ₆ , Si
F ₄ , SiFH ₃ , SiF ₂ H ₂ , SiF ₃ H, Si ₃ H ₈ ,
SiD ₄ , SiHD ₃ , SiH ₂ D ₂ , SiH ₃ D, SiF
D ₃ , SiF ₂ D ₂ , Si ₂ D ₃ H ₃ , (SiF ₂ ) ₅ , (Si
F ₂ ) ₆ , (SiF ₂ ) ₄ , Si ₂ F ₆ , Si ₃ F ₈ , Si ₂ H ₂
F ₄ , Si ₂ H ₃ F ₃ , SiCl ₄ , (SiCl ₂ ) ₅ , Si
Br ₄ , (SiBr ₂ ) ₅ , Si ₂ Cl ₆ , SiHCl ₃ , S
Examples thereof include those in a gas state or those which can be easily gasified, such as iH ₂ Br ₂ , SiH ₂ Cl ₂ , and Si ₂ Cl ₃ F ₃ .

Specific examples of the gasifiable compound containing a germanium atom include GeH ₄ , GeD ₄ , GeF ₄ ,
GeFH ₃ , GeF ₂ H ₂ , GeF ₃ H, GeHD ₃ , Ge
H ₂ D ₂ , GeH ₃ D, Ge ₂ H ₆ , Ge ₂ D _{6 and the} like.

Further, as the element for expanding the band gap of the i-type semiconductor layer used for forming the first p-type semiconductor layer of the photovoltaic device of the present invention, carbon, oxygen, nitrogen and the like can be mentioned.

Specific examples of the gasizable compound containing a carbon atom include CH ₄ , CD ₄ and C _n H _{2n + 2} (n is an integer).
C _n H _{2n (n} is an _{integer), C 2 H 2, C} 6 H 6, CO 2, CO , and the like.

As the nitrogen-containing gas, N ₂ , NH ₃ , N
D ₃ , NO, NO ₂ , and N ₂ O.

As the oxygen-containing gas, O ₂ , CO, CO ₂ ,
NO, NO ₂ , N ₂ O, CH ₃ CH ₂ OH, CH ₃ OH and the like.

Examples of substances introduced into the p-type layer or the n-type layer for controlling valence electrons include Group III atoms and Group III atoms in the periodic table.

As the starting material for introducing a group III atom effectively, specifically, for introducing a boron atom, B ₂ H ₆ , B ₄ H ₁₀ , B ₅ H ₉ , B ₅ H ₁₁ , B
Borohydrides such as ₆ H ₁₀ , B ₆ H ₁₂ , B ₆ H ₁₄ , BF ₃ , B
Halogenated boron, such as Cl ₃ , may be mentioned. In addition, AlCl ₃ , GaCl ₃ , InCl ₃ , T
1Cl _{3 and the} like can also be mentioned. Particularly, B ₂ H ₆ and BF ₃ are suitable.

Effectively used as a starting material for introducing a group V atom is, specifically, PH for introducing a phosphorus atom.
₃ , hydrogenated phosphorus such as P ₂ H ₄ , PH ₄ I, PF ₃ , PF ₅ , PC
and phosphorus halides such as l ₃ , PCl ₅ , PBr ₃ , PBr ₅ and PI ₃ . In addition, AsH ₃ , AsF ₃ , AsC
l ₃ , AsBr ₃ , AsF ₅ , SbH ₃ , SbF ₃ , Sb
_{F 5, SbCl 3, SbCl 5} , BiH 3, BiCl 3, B
iBr _{3 and the} like can also be mentioned. Particularly, PH ₃ and PF ₃ are suitable.

Further, the compound capable of being gasified is H ₂ , H
The gas may be appropriately diluted with a gas such as e, Ne, Ar, Xe, or Kr and introduced into the deposition chamber.

Particularly, a microcrystalline or polycrystalline semiconductor or a-S
When depositing a layer having a small light absorption or a wide band gap such as iC: H, the source gas is diluted 2 to 100 times with hydrogen gas, and a relatively high microwave power or RF power is introduced. Is preferred.

(Transparent Electrode) In the present invention, the transparent electrode 10
Reference numeral 7 denotes an electrode on the light incident side that transmits light, and also functions as an anti-reflection film by optimizing the film thickness. The transparent electrode 107 is required to have a high transmittance in a wavelength region where the semiconductor layer can absorb light and a low resistivity. Preferably, the transmittance at a wavelength of 550 nm or more is 80% or more, more preferably 8% or more.
It is desirable that it be 5% or more. The resistivity is preferably 5 × 10 ⁻³ Ωcm or less, more preferably 1 × 1 ⁻³ Ωcm.
Desirably, it is 0 ⁻³ Ωcm or less. The materials include In ₂ O ₃ , SnO ₂ , and ITO (In ₂ O ₃ + Sn).
O ₂ ), ZnO, CdO, Cd ₂ SnO ₄ , TiO ₂ , Ta
A conductive oxide such as ₂ O ₅ , Bi ₂ O ₃ , MoO ₃ , Na _x WO ₃ or a mixture thereof is preferably used.
Further, an element (dopant) that changes the conductivity may be added to these compounds.

As the element (dopant) for changing the conductivity, for example, when the transparent electrode 107 is ZnO, A
l, In, B, Ga, Si, F, etc .; In the case of In ₂ O ₃ , Sn, F, Te, Ti, Sb, Pb, etc .; and in the case of SnO ₂ , F, Sb, P, As, In, T
1, Te, W, Cl, Br, I, etc. are preferably used.

The transparent electrode 107 may be formed by any of various deposition methods such as EB deposition and sputter deposition, and various C methods.
A VD method, a spray method, a spin-on method, a dipping method and the like are preferably used.

(Current collecting electrode) In the present invention, the current collecting electrode 1
Reference numeral 08 is formed on a part of the transparent electrode 107 as necessary when the resistivity of the transparent electrode 107 cannot be sufficiently reduced, and serves to reduce the electrode resistivity and reduce the series resistance of the photovoltaic element. Examples of the material include metals such as gold, silver, copper, aluminum, nickel, iron, chromium, molybdenum, tungsten, titanium, cobalt, tantalum, niobium, and zirconium; alloys such as stainless steel; and conductive materials using powdered metals. Paste and the like. Then, the shape is formed in a branch shape as shown in FIG. 4, for example, so as not to block incident light on the semiconductor layer as much as possible.

Further, in the entire area of the photovoltaic device,
The area occupied by the collecting electrode is preferably 15% or less, more preferably 10% or less, and most preferably 5% or less.
In addition, a mask is used to form the pattern of the collecting electrode,
As a forming method, an evaporation method, a sputtering method, a plating method, a printing method, or the like is used.

When a photovoltaic device (module or panel) having a desired output voltage and output current is manufactured using the photovoltaic device of the present invention, the photovoltaic devices of the present invention are connected in series or in series. They are connected in parallel, protective layers are formed on the front and back surfaces, and output output electrodes and the like are attached. At this time, the polycrystalline substrate on which the photovoltaic element is formed may be disposed on another supporting substrate. When the photovoltaic elements of the present invention are connected in series, a diode for preventing backflow may be incorporated.

[0134]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the photovoltaic element of the present invention will be described in detail by manufacturing a photovoltaic element and a photodiode made of a non-single-crystal silicon-based semiconductor material, but the present invention is not limited to these. .

(Example 1) In this example, an acid treatment method was used for etching the substrate surface, and SUS was used for the substrate material.
Using a 430BA plate, a photovoltaic element having the configuration shown in FIG. 1 was produced.

Hereinafter, description will be made in accordance with the manufacturing procedure.

(1) The procedure was started from the production of the substrate. Thickness 0.2
A 50 mm × 50 mm ² SUS430BA plate was ultrasonically cleaned with acetone and isopropanol and dried with hot air to completely remove the oil and fat components remaining on the substrate surface.

Next, a stainless steel plate was set on a Teflon-made substrate holder (not shown) in order to perform an etching process on the substrate surface, and as shown in Table 1, hydrofluoric nitric acid (molar ratio HF: HNO ₃ : H ₂ O = 1: 3: 20
The substrate holder was arranged such that the substrate was sufficiently immersed in a container (not shown) containing acid composed of 0).

(2) The container containing the acid was set in a magnetic stirrer (not shown) and stirred for 5 minutes to perform a surface treatment.

(3) A part of the substrate subjected to the acid treatment was left for evaluation (Sample 1-1), and the other substrate was subjected to the formation of a reflective layer by a sputtering apparatus.

(4) An Al light reflecting layer was formed using a DC magnetron sputtering apparatus shown in FIG. The SUS430BA plate 502 subjected to the acid treatment was brought into close contact with the heater 503 in FIG. 5, and the deposition chamber 501 was evacuated from an exhaust port connected to an oil diffusion pump. When the pressure reached 1 × 10 ⁻⁶ , the valve 514 was opened, the mass flow controller 516 was adjusted, Ar gas was introduced at 50 sccm, and the conductance valve 513 was adjusted so that the pressure became 7 mTorr. A current is passed through the toroidal coil, and -400 V DC power is
1 was applied to the target 504 to generate Ar plasma.

(5) The target shutter 507 was opened to form an Al light reflection layer having a thickness of 0.3 μm on the surface of the stainless steel plate. When the Al light reflection layer was formed, the shutter was closed and the plasma was extinguished to complete the production of the Al reflection layer.

(6) A ZnO thin film layer was formed by the same method as that for forming the reflection layer. Ar gas was introduced into the deposition chamber at a flow rate of 40 sccm, the substrate temperature was set to 200 ° C., the pressure was set to 5 mTorr, and a DC power of −500 V from a sputtering power supply 510 was applied to the ZnO target 508 to generate Ar plasma.

(7) The target shutter 511 was opened, and when a ZnO thin film layer having a thickness of 1.0 μm was formed on the surface of the reflective layer, the shutter was closed to extinguish the plasma.

(8) At the stage when the transparent conductive layer was formed, a part of the substrate was left for evaluation (Sample 1-2), and the other substrates were formed with a semiconductor device using a CVD apparatus.

(9) An n-layer, an i-layer, and a p-layer were sequentially formed on the ZnO thin film layer by a multi-chamber separation type deposition apparatus shown in FIG. a
-Si layer and μc-Si p layer are RF
The i-layer formed by PCVD and made of a-Si is RFPC
It was formed by the VD method and the MWPCVD method. The production procedure was performed as follows.

(9-1) All transport systems and deposition chambers are
^A vacuum was drawn on a ^-6 Torr table. The substrate was set on the substrate holder 690 and placed in the load lock chamber 601. The load lock chamber was evacuated to a vacuum of the order of 10 ^-3 Torr with a mechanical booster pump / rotary pump (not shown), and switched to a turbo molecular pump to evacuate the pressure to the order of 10 ^-6 Torr. The gate valve 606 was opened, and the substrate holder 690 was transferred to the n-type layer transfer chamber 602. The gate valve 606 is closed. The substrate was moved under the heater 610 for substrate heating, and hydrogen gas was flowed to make the pressure substantially the same as the pressure at the time of film formation. The substrate was heated to the temperature shown in Table 1 by the heater 610 for substrate heating and stabilized. Mass flow controller 63
6-639, stop valves 630-634, 641-
At 644, the source gases shown in Table 1 for n-type layer deposition were supplied to the deposition chamber. The RF power shown in Table 1 was supplied from the RF power supply 622 to the RF introduction cup 620. An n-type layer having a thickness shown in Table 1 was deposited for a desired deposition time.

(9-2) The supply of the source gas for n-type layer deposition was stopped, and the gas was evacuated to a degree of vacuum of the order of 10 ^-6 Torr by a turbo-molecular pump. The substrate heating heater 610 is raised, the gate valve 607 is opened, and the substrate holder is set to the MW-i.
Alternatively, it has moved to the RF-i transfer chamber 603. Gate valve 607 was closed. The substrate was conveyed under the heater 611 for substrate heating, the heater 611 for substrate heating was lowered, and the substrate was heated to the substrate temperature shown in Table 1 and stabilized. RF-i
Layers were deposited. The RF-i layer is deposited in the deposition chamber 618 by MW-i.
Alternatively, a gas supply facility for RF-i layer deposition (gas supply pipe 64
9, stop valves 650-655, 661-665,
Mass flow controllers 656-660) to RF-
Source gases shown in Table 1 for i-layer deposition were supplied. RF-i
It was adjusted with an exhaust pump so that the degree of vacuum shown in Table 1 for layer deposition was obtained. A desired RF power was introduced from an RF power supply (not shown) to the bias application electrode 628, and an RF-i layer was deposited on the n-type layer to a thickness shown in Table 1 by an RF plasma CVD method.

(9-3) The supply of the source gas was stopped, and the inside of the deposition chamber was evacuated to a level of 10 ^-6 Torr by a turbo molecular pump. At the same time, the substrate temperature was set and maintained at a temperature shown in Table 1 suitable for the deposition of the MW-i layer. The source gas shown in Table 1 suitable for the deposition of the MW-i layer was supplied to the deposition chamber 618 from a gas supply facility for MW-i or RF-i layer deposition. The degree of vacuum in the deposition chamber was maintained at the degree shown in Table 1 by an exhaust device such as a diffusion pump (not shown). Table 1 from MW power supply not shown
Is introduced into the deposition chamber 618. At the same time, a bias power shown in Table 1 was introduced from a not-shown RF power supply to the bias electrode 628. The shutter 627 was opened and an MW-i layer was deposited on the substrate by the microwave plasma CVD method of the present invention.

(9-3) After that, source gases shown in Table 1 suitable for the deposition of the MW-i layer are supplied from the gas supply equipment for depositing the MW-i or RF-i layer to the deposition chamber 618, and a predetermined layer thickness is obtained. After forming the MW-i layer, the shutter was closed, the MW power and the like were stopped, and the supply of the source gas was stopped. In the deposition chamber 618,
The gas was evacuated to a level of 10 ^-6 Torr by a turbo molecular pump. In the same manner as the deposition of the RF-i layer, the RF-i
An i-layer was deposited under the conditions shown in Table 1.

(9-4) 10 ⁻⁶ T After Deposition of RF-i Layer
The deposition chamber was evacuated to the orr level. Substrate heating heater 6
11 is separated from the substrate, the gate valve 608 is opened, and the substrate holder 690 is moved to the p-type layer transfer chamber 604. The gate valve 608 is closed, the substrate is moved under the substrate heating heater 612, the substrate temperature is set to the substrate temperature shown in Table 1, and the substrate is stabilized. The p-type layer deposition gas was supplied to the deposition chamber 619 from the p-type layer deposition gas supply equipment (stop valves 670 to 674, 681 to 684, mass flow controllers 676 to 679). The degree of vacuum in the deposition chamber was adjusted to a degree shown in Table 1 by an exhaust pump (not shown). Table 1 from RF power supply 623 to RF introduction cup 621
Was applied, and a p-type layer was deposited to a thickness shown in Table 1 by an RF plasma CVD method. Pin as above
The structure is formed on a substrate.

[0152] (10) Next, stop the flow of gas, 5 minutes, vacuum after continued to flow H ₂ gas, stopping the inflow of the H ₂ gas, the deposition chamber and the gas in the pipe up to 1 × 10 ^-5 Torr Evacuation was performed, and the substrate was moved to the unload chamber 605. After sufficiently cooling the substrate, it was taken out.

(11) Next, ITO shown in Table 1 was vacuum-deposited on the p-layer as a transparent electrode by a resistance heating vacuum deposition method. Then, a mask having a comb-shaped hole was placed on the transparent electrode, and as shown in Table 1, a comb-shaped current collecting electrode made of Cr / Ag / Cr was vacuum-deposited by an electron beam vacuum deposition method.

Thus, the fabrication of the photovoltaic device having the structure shown in FIG. 1 has been completed. This photovoltaic element was called (actual 1).

[0155]

[Table 1] (Comparative Example 1-1) In this example, when performing the surface treatment of the substrate, the acid treatment time by stirring was set to 10 seconds.
And different.

The other conditions were the same as in Example 1, and samples (sample ratio 1-1), (sample ratio 1-4) and a photovoltaic element (ratio 1-1) were produced.

(Comparative Example 1-2) The present example is different from Example 1 in that the temperature of the acid treatment by ultrasonic waves was set to 80 ° C. when performing the surface treatment of the substrate.

The other conditions were the same as in Example 1, and samples (sample ratio 1-2), (sample ratio 1-5) and photovoltaic elements (ratio 1-1) were produced.

(Comparative Example 1-3) This example is different from Example 1 in that the time of the acid treatment by ultrasonic waves was set to 60 minutes when performing the surface treatment of the substrate.

The other conditions were the same as in Example 1, and samples (sample ratio 1-3), (sample ratio 1-6) and photovoltaic elements (ratio 1-1) were produced.

Hereinafter, Example 1 and Comparative Example 1-
1. Substrates subjected to surface treatment in Comparative Examples 1-2 and 1-3, ie, (Sample 1-1), (Sample ratio 1-1), (Sample ratio 1-2), (Sample ratio) 1-
The result of evaluating 3) will be described. First, the surface shape was observed with an electron microscope (SEM).
The results of examining the crystal grain size are described. Further, the surface of the substrate (the maximum peak-to-peak value, hereinafter referred to as “R
max ”) and determine the Rm of the polycrystalline grains with a textured structure.
difference between ax and Rmax of flat polycrystalline grains (referred to as Rmax (difference))
I asked. Further, from these results, the schematic shape of the cross section of the substrate was examined.

Table 2 shows the results.

[0163]

[Table 2] The SEM image of (Sample 1-1) is as shown in FIG. 3, in which the surface is divided into a portion having irregularities and a flat portion for each crystal grain.
While there is a difference in x, in (sample ratio 1-1), the crystal grains are entirely flat and there is no difference in Rmax, and in (sample ratio 1-2) and (sample ratio 1-3), The entire structure had a pyramid-shaped uneven structure, and there was no difference in Rmax.

Hereinafter, the first embodiment and the first comparative example will be described.
1, the substrates prepared up to the transparent conductive layer in Comparative Examples 1-2 and 1-3, that is, (Sample Actual 1-2), (Sample Ratio 1-4), (Sample Ratio 1-5), (Sample Ratio) The result of evaluating the ratio 1-6) will be described. First,
The surface shape was observed with an electron microscope (SEM), and the ZnO crystal grain size was examined. Further, the total reflectance and the irregular reflectance were obtained for each sample using a spectrophotometer equipped with an integrating sphere.

Table 3 shows the results.

[0166]

[Table 3] In (Sample 1-1), as shown in Table 3, the crystal grain size of ZnO forming the transparent conductive layer is large, and both total reflectance / diffuse reflectance are excellent, whereas (Sample ratio 1-4) is excellent. The crystal grain size is small and the irregular reflectance is low.
5) and (sample ratio 1-6), both the total reflectance and the irregular reflectance were extremely low.

Hereinafter, Example 1 and Comparative Example 1-
1, the photovoltaic elements produced in Comparative Examples 1-2 and 1-3, namely (actual-1), (ratio 1-1), (ratio 1)
-2) and (Comparative 1-3) are described below. First, five photovoltaic elements were manufactured, and all the photovoltaic elements were further divided into 25 subcells, and then the shunt resistance was measured in a dark place with a reverse bias voltage of -1.0 V applied. The reference value of the shunt resistor is 4 × 10 ⁴
Ωcm ² and the yield was examined. Subsequently, an adhesion test, initial photoelectric conversion efficiency (photovoltaic power / incident optical power), photodegradation, high-temperature high-humidity reverse bias (HHRB) degradation, and temperature-humidity degradation were measured.

In the adhesion test, a photovoltaic element prepared by a grid tape method was laid in a grid pattern at intervals of 1 mm.
Make 0 incisions and 100 squares.
The cellophane adhesive tape was adhered, and after sufficiently adhered, it was instantaneously peeled off, and the area of the peeled portion was evaluated.

The measurement of the initial photoelectric conversion efficiency can be obtained by placing the produced photovoltaic element under irradiation of AM-1.5 (100 mW / cm ² ) light and measuring the VI characteristics.

The photodegradation was measured by measuring the initial photovoltaic conversion efficiency of a photovoltaic element at a humidity of 50% and a temperature of 25%.
C. environment, and the rate of decrease in photoelectric conversion efficiency under AM1.5 light irradiation (photoelectric conversion efficiency after light degradation test / initial photoelectric conversion efficiency) after 500 hours of AM-1.5 light irradiation. went.

The measurement of high temperature and high humidity reverse bias (HHRB) deterioration is performed by installing a photovoltaic element in which the initial photoelectric conversion efficiency is measured in advance in a dark place at a temperature of 85 ° C. and a humidity of 85%, and applying the photovoltaic element to the photovoltaic element. Apply a reverse bias of 0.7 V and hold for 100 hours,
Reduction rate of photoelectric conversion efficiency under subsequent AM1.5 light irradiation (photoelectric conversion efficiency after vibration degradation test / initial photoelectric conversion efficiency)
Was performed.

The measurement of the temperature and humidity deterioration is performed by measuring the initial photoelectric conversion efficiency of a photovoltaic element at a temperature of 85 ° C. and a humidity of 8 ° C.
This cycle was repeated 100 times in a dark place of 5% and maintained for 30 minutes, then lowered to a temperature of −20 ° C. for about 70 minutes and maintained for 30 minutes, and returned to 85 ° C. and 85% humidity again for 70 minutes. Rate of decrease in photoelectric conversion efficiency under AM1.5 light irradiation (photoelectric conversion efficiency after vibration degradation test /
(Initial photoelectric conversion efficiency).

Table 4 shows the results.

[0174]

[Table 4] As a result of the measurement, (ratio 1-1) was lower in yield and adhesion than (actual-1). Although the photoelectric conversion efficiencies after each deterioration test are also inferior, these differences are mainly due to a decrease in FF due to a decrease in series resistance due to adhesion. (Comparative 1-2), (Comparative 1-)
In 3), the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after each deterioration were all low values. Regarding the initial photoelectric conversion efficiency, the short-circuit current (Js
c) was decreased, and the photoelectric conversion efficiency after each deterioration was mainly due to a decrease in the open circuit voltage (Voc).

As described above, the photovoltaic device of the present invention (actual-
1) is a conventional photovoltaic element (ratio 1-1), (ratio 1-
2) It was found to have characteristics superior to (ratio 1-3).

Example 2 In this example, a photovoltaic element having the structure shown in FIG. 1 was manufactured by using RF sputtering as an etching process for a substrate surface and using a SUS430-2B plate as a substrate material.

Hereinafter, description will be made in accordance with the manufacturing procedure.

(1) US430-2B as in Example 1
After the oil and fat components on the plate were completely removed, the surface of the substrate was etched using a sputtering apparatus shown in FIG. The substrate 502 was brought into close contact with the heater 503 in FIG. 5, and the processing chamber 501 was evacuated from the exhaust port. Pressure 1
When the pressure becomes × 10 ⁻⁶ , the valve 514 is opened, and the mass flow controller 516 is adjusted to supply Ar gas for 50 seconds.
Ccm was introduced, and the pressure was adjusted with a conductance valve 513 so as to be 6 mTorr. Sputter power supply 506
From 200 W was applied to the substrate to generate Ar plasma. After maintaining the Ar plasma for 20 minutes, the plasma was extinguished, and the etching process was completed.

(2) A part of the etched substrate was left for evaluation (Sample 2-1), and the other substrates were formed with the Al reflective layer under the conditions shown in Table 5 in the same manner as in Example 1. Was done.

(3) Then, similarly to Example 1, a ZnO transparent electrode layer was formed under the conditions shown in Table 5, and a part of the substrate was left for evaluation (Sample 2-2), and the other substrates were CV
D device, the pin-type semiconductor layer, In
₂ O ₃ transparent electrode, to form a collecting electrode photovoltaic device (actual -
2) was produced.

[0181]

[Table 5] (Comparative Example 2-1) This example is different from Example 2 in that the processing time by RF sputtering was set to 20 seconds when performing the surface treatment of the substrate.

The other points were the same as in Example 2, and samples (sample ratio 2-1), (sample ratio 2-4) and a photovoltaic element (ratio 2-1) were produced.

(Comparative Example 2-2) In this example, the point that the substrate temperature was set to 300 ° C. when the surface treatment of the substrate was performed was set to the second embodiment.
And different.

The other conditions were the same as in Example 2, and samples (sample ratio 2-2), (sample ratio 2-5) and a photovoltaic element (ratio 2-2) were produced.

(Comparative Example 2-3) In this example, when performing the surface treatment of the substrate, the processing time by RF sputtering was set to 9 hours.
The difference from Example 2 is that the time is set to 0 minutes.

The other conditions were the same as in Example 2, and samples (sample ratio 2-3), (sample ratio 2-6) and photovoltaic elements (ratio 2-3) were produced.

In the following, the substrates subjected to the surface treatment in the same manner as in Example 1, that is, (sample actual 2-1), (sample ratio 2-1), (sample ratio 2-2), (sample ratio 2-2)
The results of the evaluation of (-3) will be described. Example 1
In the same manner as described above, the surface shape is observed, the crystal grain size is examined, and the substrate surface roughness (maximum peak-to-peak value, hereinafter referred to as “Rma
x ”), the difference of Rmax (referred to as Rmax (difference)) was determined, and the schematic shape of the substrate cross section was examined.

The results are shown in Table 6.

[0189]

[Table 6] In the same manner as in Example 1 (Sample Sample 2-2), the surface is divided into irregular portions and flat portions for each crystal grain as shown in Table 6, and Rmax of the irregular portion and the flat portion is While there is a difference, in (sample ratio 1-1) the crystal grains are generally flat and there is no difference in Rmax, and in (sample ratio 1-2) and (sample ratio 1-3), It has a pyramid-shaped uneven structure, and Rmax has no difference.

In the following, the substrates prepared up to the transparent conductive layer in the same manner as in Example 1, ie, (Sample 2-2), (Sample ratio 2-4), (Sample ratio 2-5), (Sample ratio 2-5) The result of evaluating 6) will be described. In the same manner as in Example 1, the surface shape was observed, the ZnO crystal grain size was checked, and the respective total reflectance and diffuse reflectance were obtained using a spectrophotometer equipped with an integrating sphere.

The results are shown in Table 7.

[0192]

[Table 7] In the same manner as in Example 1 (Sample Sample 2-2), as shown in Table 7, the crystal grain size of ZnO forming the transparent conductive layer was large, and both total reflectance / diffuse reflectance were excellent. In the ratio 2-4), the crystal grain size is small and the irregular reflectance is low,
In (sample ratio 2-5) and (sample ratio 2-6), both the total reflectance and the irregular reflectance were very low.

In the following, similarly to Example 1, the above-described Example 2, Comparative Example 2-1, Comparative Example 2-2, and Comparative Example 2-
The results of the evaluation of the photovoltaic element manufactured in No. 3, that is, (real-2), (ratio 2-1), (ratio 2-2), and (ratio 2-3) will be described. First, each of the five sub-cells was manufactured, and then divided into 25 sub-cells.
The shunt resistance was measured with a reverse bias voltage of 1.0 V applied. The reference value of the shunt resistor is 4 × 10 ⁴ Ωcm ²
Then, the yield was checked. Further, in the same manner as in Example 1, an adhesion test, measurement of initial photoelectric conversion efficiency (photovoltaic power / incident light power), photodegradation, high-temperature high-humidity reverse bias (HHRB) degradation, and temperature-humidity degradation were performed.

Table 8 shows the results.

[0195]

[Table 8] As a result of the measurement, (ratio 2-1) was lower in yield and adhesion than (real-2). Although the photoelectric conversion efficiencies after each deterioration test are also inferior, these differences are mainly due to a decrease in FF due to a decrease in series resistance due to adhesion. (Ratio 2-2), (ratio 2-
In 3), the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after each deterioration were all low values. Regarding the initial photoelectric conversion efficiency, the short-circuit current (Js
c) was decreased, and the photoelectric conversion efficiency after each deterioration was mainly due to a decrease in the open circuit voltage (Voc).

As described above, the photovoltaic device of the present invention (actual
2) are conventional photovoltaic elements (ratio 2-1), (ratio 2-
2) and (ratio 2-3) were found to have better characteristics.

(Embodiment 3) In this embodiment, an acid treatment method is used for etching the substrate surface, and SUS is used for the substrate material.
Using the 430-2D plate, a photovoltaic element having the configuration shown in FIG. 1 was produced.

Hereinafter, description will be made in accordance with the manufacturing procedure.

(1) As in Example 1, US430-2D
The surface of the substrate was etched using the acid shown in Table 9 on the plate.

(2) A part of the substrate subjected to the etching treatment was evaluated (Sample 3-1), and an Al reflective layer was formed under the conditions shown in Table 9 in the same manner as in Example 1.

(3) After forming the Al reflective layer, a part of the substrate was left for evaluation, a ZnO transparent electrode layer was formed under the conditions shown in Table 9, and a part of the substrate was left for evaluation (sample Real 3
-2).

(4) The other substrates were formed by a CVD apparatus under the conditions shown in Table 9 under the conditions of a pin semiconductor layer, an In ₂ O ₃ transparent electrode,
A current collecting electrode was formed to produce a photovoltaic element (actual-3).

[0203]

[Table 9] (Comparative Example 3-1) In this example, when the surface treatment of the substrate is performed, the mixing ratio of hydrofluoric acetic acid is changed to (HF: HNO ₃ : H ₂ O:
CH ₃ COOH = 1: 3: 3: 500).

The other conditions were the same as in Example 3, except that the samples (sample ratio 3-1), (sample ratio 3-5), (sample ratio 3-9) and the photovoltaic element (ratio 3-1) were used. Was prepared.

(Comparative Example 3-2) In the present example, the point that the thickness of the deposited layer was 3000 nm when depositing the reflective layer was the same as in Example 3.
And different.

The other conditions were the same as in Example 3, except that the sample (sample ratio 3-2), (sample ratio 3-6), (sample ratio 3-10) and the photovoltaic element (ratio 3-2) Was prepared.

(Comparative Example 3-3) This example is different from Example 3 in that the substrate temperature was set to 150 ° C. when depositing the reflective layer.

The other conditions were the same as in Example 3, except that the samples (sample ratio 3-3), (sample ratio 3-7), (sample ratio 3-11) and the photovoltaic element (ratio 3-3) Was prepared.

(Comparative Example 3-4) This example is different from Example 3 in that the surface treatment of the substrate was performed with an acid treatment time of 90 minutes.

The other conditions were the same as in Example 3, except that the samples (sample ratio 3-4), (sample ratio 2-8), (sample ratio 3-12) and the photovoltaic element (ratio 3-4) Was prepared.

In the following, the substrates subjected to the surface treatment in the same manner as in Example 1, that is, (Sample 3-1), (Sample ratio 3-1), (Sample ratio 3-2), (Sample ratio 3-2)
-3) and (Sample ratio 3-4) are described below. In the same manner as in Example 1, the surface shape was observed, the crystal grain size was checked, and the difference (Rmax) from the substrate surface roughness (maximum peak toe peak value, hereinafter “Rmax”) was calculated.
(To be referred to as (difference))), and the schematic shape of the substrate cross section was examined. In addition, for each sample, the approximate shape of the cross section of the substrate after forming the reflective layer (referred to as the approximate surface shape (anti)) was examined at exactly the same place as that observed on the substrate surface with an electron microscope.

The results are shown in Table 10.

[0213]

[Table 10] In the same manner as in Example 1 (Sample Sample 3-1), the surface is divided into a portion having irregularities and a flat portion for each crystal grain as shown in Table 10, and the step on the surface of the substrate subjected to the etching treatment is reflected on the reflection layer. While the shape of R is reflected as it is and inherits the difference in Rmax between the uneven part and the flat part,
In (sample ratio 3-1), the crystal grains are generally flat and there is no difference in Rmax. In (sample ratio 3-2) and (sample ratio 3-3), the structure seen on the substrate surface is changed on the reflection layer surface. Did not reflect. Also, (sample ratio 3-4) had a pyramid-shaped uneven structure as a whole, and there was no difference in Rmax for each crystal grain.

The substrates (sample 3-5), (sample ratio 3-6), (sample ratio 3-7), and (sample ratio 3-8) prepared up to the transparent conductive layer have ZnO crystal grain sizes. Was examined to determine the total reflectance and the irregular reflectance.

The results are shown in Table 11.

[0216]

[Table 11] In the same manner as in Example 1 (Sample 3-2), as shown in Table 11, the crystal grain size of ZnO forming the transparent conductive layer was large,
While the total reflectance / diffuse reflectance is excellent, both (sample ratio 3-5) and (sample ratio 3-6) have a small crystal grain size and low diffuse reflectance, and (sample ratio 3-7), (sample ratio 3-7). In the sample ratio 3-8), both the total reflectance and the irregular reflectance were extremely low.

In the following, similarly to Example 1, the above-described Example 3, Comparative Example 3-1, Comparative Example 3-2, Comparative Example 3-3,
And the photovoltaic elements produced in Comparative Example 3-4, ie, (actual-3), (ratio 3-1), (ratio 3-2), (ratio 3-2)
The results evaluated for 3) and (ratio 3-4) will be described. First, five cells were manufactured, and the cells were further divided into 25 subcells, and the yield was examined. Example 1
In the same manner as described above, adhesion test, initial photoelectric conversion efficiency (photovoltaic power / incident optical power), photodegradation, high temperature and high humidity reverse bias (HHR)
B) Deterioration and temperature / humidity deterioration were measured.

The results are shown in Table 12.

[0219]

[Table 12] As a result of the measurement, (ratio 3-1) and (ratio 3)
-2) was a low value in yield and adhesion. Although the photoelectric conversion conversion efficiencies after each deterioration test are also inferior, these differences are mainly due to a decrease in FF due to a decrease in series resistance due to adhesion. (Comparative 3)
In (3) and (Comparative 3-4), the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after each deterioration were all low values. The initial photoelectric conversion efficiency was due to a decrease in short-circuit current (Jsc) due to a decrease in total reflectance and irregular reflectance, and the photoelectric conversion efficiency after each deterioration was mainly due to a decrease in open-circuit voltage (Voc). .

As described above, the photovoltaic device of the present invention (actual
3) is a conventional photovoltaic element (Comparative 3-1), (Comparative 3-
2), (Comparative 3-3) and (Comparative 3-4) were found to have superior characteristics.

Example 4 In this example, as in Example 3, an acid treatment method was used for etching the substrate surface, a SUS430-2D plate was used as the substrate material, and a photovoltaic device having the structure shown in FIG. A power element was manufactured.

Hereinafter, description will be made in accordance with the manufacturing procedure.

(1) As in Example 3, US430-2D
An etching treatment was performed on the board surface using the acid shown in Table 13.

(2) A part of the substrate that had been subjected to the etching treatment was evaluated (Sample 4-1), and then an Ag reflection layer was formed under the conditions shown in Table 13 in the same manner as in Example 3.

(3) After forming the Ag reflective layer, a ZnO transparent electrode layer was formed under the conditions shown in Table 13, and a part of the substrate was left for evaluation (Sample 4-2).

(4) On the other substrates, a pin-type semiconductor layer, a transparent electrode of In ₂ O ₃ , and a current collecting electrode were formed in the same manner as in Example 3 under the conditions shown in Table 13 to produce a photovoltaic element.
4).

[0227]

[Table 13] (Comparative Example 4-1) This example is different from Example 4 in that the deposited film thickness was 3000 nm when the reflective layer was deposited.

The other conditions were the same as in Example 4, and samples (sample ratio 4-1), (sample ratio 4-4) and a photovoltaic element (ratio 4-1) were produced.

(Comparative Example 4-2) This example is different from Example 4 in that the substrate temperature was set to 300 ° C. when depositing the reflective layer.

The other conditions were the same as in Example 4, and samples (sample ratio 4-2), (sample ratio 4-5) and photovoltaic elements (ratio 4-2) were produced.

(Comparative Example 4-3) This example is different from Example 4 in that the surface treatment of the substrate was performed with an acid treatment time of 100 minutes.

The other conditions were the same as in Example 4, and samples (sample ratio 4-3), (sample ratio 4-6) and photovoltaic elements (ratio 4-3) were produced.

In the following, the substrates subjected to the surface treatment in the same manner as in Example 3, ie, (sample ratio 4-1), (sample ratio 4-1), (sample ratio 4-2), (sample ratio 4
The results of the evaluation of (-3) will be described. Observation of the surface shape was performed, and the crystal grain size and substrate surface roughness (Rma
x), the difference of Rmax (Rmax (difference)) was determined, and the schematic shape of the substrate cross section (referred to as a schematic surface shape (base)) was examined. In each sample, the outline of the cross section of the substrate after formation of the transparent conductive layer (referred to as the outline surface shape (transparent)) was observed at exactly the same place where the surface of the substrate was observed with an electron microscope.

The results are shown in Table 14.

[0235]

[Table 14] In the same manner as in Example 1 (Sample Sample 4-1), the surface is divided into a portion having irregularities and a flat portion for each crystal grain as shown in Table 14, and the shape of the transparent conductive layer is determined by the etching-treated substrate. While the step of the surface is reflected as it is and the difference in Rmax between the uneven portion and the flat portion is inherited, in (sample ratio 4-1) and (sample ratio 4-2), the substrate is provided for each crystal grain. Although it is divided into a portion having unevenness and a flat portion, its shape is not reflected in the transparent conductive layer, and (sample ratio 4-3) has a pyramid-shaped uneven structure as a whole, and Rmax also differs. There was no one.

Also, the samples prepared up to the transparent conductive layer in the same manner as in Example 3, ie, (Sample ratio 4-1), (Sample ratio 4-4), (Sample ratio 4-5), (Sample ratio 4-6) Regarding (2), the surface shape was observed, and the ZnO crystal grain size, total reflectance, and irregular reflectance were determined.

The results are shown in Table 15.

[0238]

[Table 15] As in Example 3 (Sample Sample 4-2), the crystal grain size of ZnO forming the transparent conductive layer is large, and both total reflectance / diffuse reflectance are excellent.
In Example 2, the crystal grain size was small and the irregular reflectance was low.
-5) and (sample ratio 4-6), both the total reflectance and the irregular reflectance were very low.

In the following, as in Example 3, the above-described Example 4, Comparative Example 4-1, Comparative Example 4-2, and Comparative Example 4-
The results of evaluating the photovoltaic elements manufactured in No. 3, that is, (Comparative-4), (Comparative 4-1), (Comparative 4-2), and (Comparative 4-3) will be described. First, five cells were manufactured, and the cells were further divided into 25 subcells, and the yield was examined. Further, in the same manner as in Example 3, an adhesion test, initial photoelectric conversion efficiency (photovoltaic power / incident light power), light deterioration, high temperature / high humidity reverse bias (HHRB) deterioration, and temperature / humidity deterioration were measured.

The results are shown in Table 16.

[0241]

[Table 16] As a result of the measurement, (ratio 4-1) was lower in yield and adhesion than (actual-4). Although the photoelectric conversion conversion efficiencies after each deterioration test are also inferior, these differences are mainly due to a decrease in FF due to a decrease in series resistance due to adhesion. In (Comparative 4-2) and (Comparative 4-3), the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after each deterioration were all lower values than (Real-4). Regarding the initial photoelectric conversion efficiency, the short-circuit current (J
sc) decreased, and the photoelectric conversion efficiency after each deterioration was mainly due to a decrease in open circuit voltage (Voc).

As described above, the photovoltaic device of the present invention (actual-
4) is a conventional photovoltaic element (ratio 4-1),
2) It was found to have characteristics superior to (comparative 4-3).

(Embodiment 5) In this embodiment, an acid treatment method is used for etching the substrate surface, and a SUS material is used for the substrate material.
Using the 430-BA plate, a photovoltaic device having the configuration shown in FIG. 1 was produced.

Hereinafter, description will be made in accordance with the manufacturing procedure.

(1) US430-BA as in Example 4
An etching treatment of the substrate surface was performed on the plate using an acid shown in Table 17.

(2) A part of the substrate that had been subjected to the etching treatment was evaluated (Sample 5-1), and then a Cu reflection layer was formed under the conditions shown in Table 17 in the same manner as in Example 4.

(3) After forming the Cu reflection layer, a ZnO transparent electrode layer was formed under the conditions shown in Table 17, and a part of the substrate was left for evaluation (Sample 5-2).

(4) On the other substrates, a pin-type semiconductor layer, an In ₂ O ₃ transparent electrode, and a current collecting electrode were formed in the same manner as in Example 4 under the conditions shown in Table 17 to produce a photovoltaic device (actually, the same as in Example 4).
5).

A part of the photovoltaic element was left for sample evaluation.

[0250]

[Table 17] (Comparative Example 5-1) This example is different from Example 5 in that the thickness of the deposited layer was 2000 nm when the reflective layer was deposited.

The other conditions were the same as in Example 5, and samples (sample ratio 5-1), (sample ratio 5-4), and a photovoltaic element (ratio 5-1) were produced.

(Comparative Example 5-2) The present example is different from Example 5 in that the substrate temperature was set to 350 ° C. when depositing the reflective layer.

The other conditions were the same as in Example 5, and samples (sample ratio 5-2), (sample ratio 5-5) and a photovoltaic element (ratio 5-2) were produced.

(Comparative Example 5-3) This example is different from Example 5 in that the deposited film thickness was set to 10 μm when depositing the transparent conductive layer.
And different.

The other conditions were the same as in Example 5, and samples (sample ratio 5-3), (sample ratio 5-6) and a photovoltaic element (ratio 5-2) were produced.

In the following, the substrates subjected to the surface treatment in the same manner as in Example 4, ie, (sample actual 5-1), (sample ratio 5-1), (sample ratio 5-2), (sample ratio 5
The results of the evaluation of (-3) will be described. Observation of the surface shape was performed, and the crystal grain size and substrate surface roughness (Rma
x), the difference of Rmax (Rmax (difference)) was determined, and the schematic shape of the substrate cross section (referred to as a schematic surface shape (base)) was examined. In addition, for each sample, at the exact same place where the surface of the substrate was observed with an electron microscope, the schematic shape of the substrate cross section after forming the photovoltaic element (referred to as a schematic surface shape (primary)) was observed. .

The results are shown in Table 18.

[0258]

[Table 18] In the same manner as in Example 1 (Sample Example 5-1), as shown in Table 18, the surface is divided into a portion having irregularities and a flat portion for each crystal grain, and the shape on the photovoltaic element is subjected to etching. While the level difference of the substrate surface is reflected as it is, the semiconductor layer surface inherits the difference in Rmax between the uneven portion and the flat portion, whereas (sample ratio 5-1), (sample ratio 5-2), In (sample ratio 5-3), the surface shape of the substrate is not reflected in all the photovoltaic elements, and in (sample ratio 5-1), the surface shape of the photovoltaic element is relatively flat and Rmax (difference) is also small. In (sample ratio 5-2) and (sample ratio 5-3), Rmax (difference) was small due to the pyramid-shaped uneven structure.

Further, the samples prepared up to the transparent conductive layer in the same manner as in Example 4, ie, (Sample 5-1), (Sample ratio 5-4), (Sample ratio 5-5), (Sample ratio 5-6) Regarding (2), the surface shape was observed, and the ZnO crystal grain size, total reflectance, and irregular reflectance were determined.

The results are shown in Table 19.

[0261]

[Table 19] In the same manner as in Example 4 (Sample Sample 5-2), the crystal grain size of ZnO forming the transparent conductive layer was large and both total reflectance / diffuse reflectance were excellent, whereas (Sample ratio 5-4)
In (2), the crystal grain size was small (sample ratio 5-5), and in (sample ratio 5-6), both the total reflectance and the irregular reflectance were very low.

In the following, similarly to Example 4, the above-described Example 5, Comparative Example 5-1, Comparative Example 5-2, and Comparative Example 5-
The results of the evaluation of the photovoltaic device manufactured in No. 3, that is, (Comparative-5), (Comparative 5-1), (Comparative 5-2), and (Comparative 5-3) will be described. First, five cells were manufactured, and the cells were further divided into 25 subcells, and the yield was examined. Further, in the same manner as in Example 4, an adhesion test, initial photoelectric conversion efficiency (photovoltaic power / incident light power), photodegradation, high-temperature high-humidity reverse bias (HHRB) degradation, and temperature-humidity degradation were measured.

The results are shown in Table 20.

[0264]

[Table 20] As a result of the measurement, (ratio 5-1) and (ratio 5)
-3) was a low value in yield and adhesion. Although the photoelectric conversion conversion efficiencies after each deterioration test are also inferior, these differences are mainly due to a decrease in FF due to a decrease in series resistance due to adhesion. (Actual-5)
In -2), the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after each deterioration were all low values. Regarding the initial photoelectric conversion efficiency, the short-circuit current (Js
c) was decreased, and the photoelectric conversion efficiency after each deterioration was mainly due to a decrease in the open circuit voltage (Voc).

As described above, the photovoltaic device of the present invention (actual
5) is a conventional photovoltaic element (ratio 5-1), (ratio 5-
2) It was found to have better characteristics than (ratio 5-3).

(Embodiment 6) In this embodiment, the deposition apparatus using the roll-to-roll method shown in FIG.
An npinpin type solar cell was manufactured.

The substrate used was a belt-shaped SUS430BA sheet having a length of 100 m, a width of 30 cm, and a thickness of 0.15 mm.
The SUS430BA sheet was wound around a feed bobbin (not shown) in a vacuum container (not shown), and the take-up bobbin connected to one end was rotated to perform RF plasma etching with Ar plasma while feeding the SUS430BA sheet.

A portion of the etched substrate was evaluated (Sample 6-1), and the cross-sectional shape was examined (referred to as the approximate surface shape (base)). Then, the AlSi reflective layer and the Zn were formed by the roll-to-roll method under the conditions shown in Table 21.
An O transparent electrode layer was formed, and a part of the substrate was left for evaluation (Sample Sample 6-2), and the cross-sectional shape was examined (described as a rough surface shape (anti)). For other substrates, photovoltaic elements were produced by a roll-to-roll CVD apparatus under the conditions shown in Table 21 (actual-6).

Hereinafter, the deposition apparatus of FIG. 7 will be described.

FIG. 7A is a schematic diagram of an apparatus for continuously forming photovoltaic elements using a roll-to-roll method. This apparatus includes a substrate delivery chamber 729 and a plurality of deposition chambers 701.
713 and a substrate take-up chamber 730 are sequentially arranged, and connected between them by a separation passage 714. Each deposition chamber has an exhaust port, and the inside can be evacuated.

The belt-like substrate 740 passes through the deposition chamber and the separation passage, and is taken up from the substrate delivery chamber to the substrate take-up chamber. At the same time, gas can be introduced from the gas inlets of the respective deposition chambers and separation passages, and the gas can be exhausted from the respective exhaust ports to form respective layers. A halogen lamp heater 718 for heating the substrate from behind is installed in each deposition chamber, and is heated to a predetermined temperature in each deposition chamber.

FIG. 7B is a view of the deposition chambers 701 to 713 as viewed from above. Each deposition chamber has an inlet 715 and an exhaust port 716 for a source gas, and an RF electrode 717 or a microwave applicator 718 is attached. The source gas inlet 715 is connected to a source gas supply device (not shown). A vacuum exhaust pump (not shown) such as an oil diffusion pump or a mechanical booster pump is connected to an exhaust port of each deposition chamber, and an inlet 719 through which scavenging gas flows is provided in a separation passage 714 connected to the deposition chamber. A scavenging gas such as

In the deposition chambers 703 and 707, which are the deposition chambers for the MW-i layer, bias electrodes 720 are arranged, and an RF power supply (not shown) is connected as a power supply. The substrate delivery chamber has a delivery roll 721 and a guide roller 722 for applying an appropriate tension to the substrate and always keeping the substrate horizontal. The substrate take-up chamber has a take-up roll 723 and a guide roller 724.

Hereinafter, description will be made in accordance with the manufacturing procedure.

(1) First, the SUS430BA sheet is wound around a delivery roll 721 (with an average curvature radius of 3).
0 cm), set in the substrate unloading chamber 729, pass through each deposition chamber, and wrap the end of the substrate on the substrate take-up roll 72.
3 wrapped around.

(2) The entire apparatus was evacuated by a vacuum pump, the lamp heaters in each deposition chamber were turned on, and the substrate temperature in each deposition chamber was set to a predetermined temperature.

(3) When the pressure of the entire apparatus becomes 1 mTorr or less, a scavenging gas as shown in FIG. 7A is introduced from the scavenging gas inlet 719, and the substrate is wound while moving in the direction of the arrow in the figure. It was rolled up.

(4) Each source gas was flowed into each deposition chamber. At this time, the flow rate of the gas flowing into each separation passage or the pressure of each deposition chamber was adjusted so that the raw material gas flowing into each deposition chamber did not diffuse into other deposition chambers.

(5) Then, RF power or MW power and RF bias power were introduced to generate plasma.
Under the conditions shown in FIG. 1, an n1 layer is deposited as a first pin junction in the deposition chamber 701, an i1 layer is deposited in the deposition chambers 702, 703, and 704, and a p1 layer is deposited in the deposition chamber 705, and n2 is deposited as a second pin junction in the deposition chamber 706. Layer, i2 layer in deposition chambers 707, 708, 709, p2 layer in deposition chamber 710, and third pin
N3 layer in the deposition chamber 711 and i3 in the deposition chamber 712
A p3 layer was deposited in the layer and deposition chamber 713 to form a photovoltaic device consisting of a three-layer pin junction.

(6) When the winding of the substrate is completed,
All the MW power supply, RF power supply, and plasma were extinguished, and the inflow of the raw material gas and the scavenging gas was stopped. The entire device was leaked, and the take-up roll was taken out.

(7) Next, the transparent electrode 213 was formed into a three-layer pin using a reactive sputtering apparatus under the conditions shown in Table 21.
Made on the joint.

(8) Next, a layer thickness of 5 μm was obtained by screen printing.
m, a carbon paste having a line width of 0.5 mm is printed, and a silver paste having a layer thickness of 10 μm and a line width of 0.5 mm is printed thereon to form a current collecting electrode.
It was cut into a size of mx 100 mm.

In the above, n using the roll-to-roll method
The manufacture of the ipnipnip type solar cell (actual-6) was completed.

[0284]

[Table 21] (Comparative Example 6-1) This example is different from Example 6 in that the processing time by RF sputtering was set to 15 seconds when performing the surface treatment of the substrate.

The other conditions were the same as in Example 6, and samples (sample ratio 6-1), (sample ratio 6-4) and photovoltaic elements (ratio 6-1) were produced.

(Comparative Example 6-2) This example is different from Example 6 in that the substrate temperature was set to 300 ° C. during the surface treatment of the substrate.
And different.

The other conditions were the same as in Example 6, and samples (sample ratio 6-2), (sample ratio 6-5) and a photovoltaic element (ratio 6-2) were produced.

(Comparative Example 6-3) In this example, when performing the surface treatment of the substrate, the processing time by RF sputtering was set to 1 hour.
The difference from the sixth embodiment is that 00 minutes is set.

The other conditions were the same as in Example 6, and samples (sample ratio 6-3), (sample ratio 6-6) and photovoltaic elements (ratio 6-3) were produced.

In the following, the substrates subjected to the surface treatment in the same manner as in Example 1, ie, (Sample 6-1), (Sample ratio 6-1), (Sample ratio 6-2), (Sample ratio 6-2)
The results of the evaluation of (-3) will be described. Observation of the surface shape was performed, and the crystal grain size and substrate surface roughness (Rma
x), the difference of Rmax (Rmax (difference)) was determined, and the schematic shape of the substrate cross section (referred to as a schematic surface shape (base)) was examined.

The results are shown in Table 22.

[0292]

[Table 22] In the same manner as in Example 1 (Sample 6-2), the surface is divided into irregular portions and flat portions for each crystal grain as shown in Table 22, and Rmax of the irregular portion and the flat portion is determined.
In contrast, in (sample ratio 6-1), the crystal grains were entirely flat and there was no difference in Rmax. In (sample ratio 6-2) and (sample ratio 6-3), It has a pyramid-shaped uneven structure, and Rmax has no difference.

Further, the substrates prepared up to the transparent conductive layer in the same manner as in Example 1, ie, (Sample 6-2), (Sample 6-4), (Sample 6-5), (Sample 6-6)
For -6), the surface shape was observed and Zn
The O crystal grain size was checked, and the total reflectance and diffuse reflectance were determined using a spectrophotometer equipped with an integrating sphere.

The results are shown in Table 23.

[0295]

[Table 23] In the same manner as in Example 1 (Sample Sample-6), as shown in Table 23, the crystal grain size of ZnO forming the transparent conductive layer was large and both total reflectance / diffuse reflectance were excellent. In 6-4), the crystal grain size is small and the irregular reflectance is low,
In (sample ratio 6-5) and (sample ratio 6-6), both the total reflectance and the irregular reflectance were very low.

In the following, similarly to Example 5, the above-described Example 6, Comparative Example 6-1, Comparative Example 6-2, and Comparative Example 6
The results of evaluating the photovoltaic elements manufactured in No. 3, that is, (Comparative-6), (Comparative 6-1), (Comparative 6-2) and (Comparative 6-3) will be described. First, five shunt resistors were manufactured, and the shunt resistance was measured in a dark place with a reverse bias voltage of -1.0 V applied. 4x shunt resistance reference value
The yield was determined at 10 ⁴ Ωcm ² . Further, in the same manner as in Example 1, an adhesion test, measurement of initial photoelectric conversion efficiency (photovoltaic power / incident light power), photodegradation, high-temperature high-humidity reverse bias (HHRB) degradation, and temperature-humidity degradation were performed.

The results are shown in Table 24.

[0298]

[Table 24] As a result of the measurement, (ratio 6-1) was lower in yield and adhesion than (actual-6). Although the photoelectric conversion conversion efficiencies after each deterioration test are also inferior, these differences are mainly due to a decrease in FF due to a decrease in series resistance due to adhesion. In (Comparative 6-2) and (Comparative 6-3), the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after each deterioration were all lower values than (Result-6). Regarding the initial photoelectric conversion efficiency, the short-circuit current (J
sc) decreased, and the photoelectric conversion efficiency after each deterioration was mainly due to a decrease in open circuit voltage (Voc).

As described above, the photovoltaic device of the present invention (actual-
6) are conventional photovoltaic elements (ratio 6-1), (ratio 6-
2) It was found to have better characteristics than (ratio 6-3).

Example 7 In this example, as in Example 1, the substrate surface was etched using an acid, and a photovoltaic device having the configuration shown in FIG. 1 using a SUS304 mirror-finished plate as the substrate material was used. An element was manufactured.

[0301] In the same manner as in Example 1, on a SUS substrate,
The surface of the substrate was etched using the acid shown in FIG.
A portion of the etched substrate was evaluated (Sample 7-1), and then an AlAg alloy reflective layer was formed under the conditions shown in Table 25 as in Example 1. After forming the AlAg alloy reflective layer, a ZnO transparent electrode layer was formed under the conditions shown in Table 25, and a part of the substrate was left for evaluation (Sample 7-2). On other substrates, a pin-type semiconductor layer, an In ₂ O ₃ transparent electrode, and a current collecting electrode were formed under the conditions shown in Table 25 to produce a photovoltaic device (Example-7).

Next, an n-layer made of a-Si, a p-layer made of μc-Si, and an i-layer made of poly-Si were sequentially formed on the ZnO thin film layer by a multi-chamber separation type deposition apparatus (not shown).

Hereinafter, description will be made in accordance with the manufacturing procedure.

(1) First, using the same apparatus as in Embodiment 1, Zn
An n-layer made of a-Si was deposited on the O thin film layer.

(2) Next, H using a double tube (not shown)
Using a deposition apparatus (not shown) by the RCVD method, Table 25 was used.
An i-layer made of poly-Si was deposited under the following conditions.

(3) Further, using the same apparatus as in Example 1, a p-layer made of μc-Si was deposited.

(4) Thereafter, as in Example 1, an In ₂ O ₃ transparent electrode and a current collecting electrode were formed under the conditions shown in Table 25, thereby producing a photovoltaic element (Example-7).

[0308]

[Table 25] (Comparative Example 7-1) The present example is different from Example 7 in that the surface treatment of the substrate was performed with an acid for 15 seconds.

Except for this point, samples (sample ratio 7-1), (sample ratio 7-4) and photovoltaic element (ratio 7-1) were manufactured under the same conditions as in Example 7.

(Comparative Example 7-2) This example is different from Example 7 in that the acid solution temperature was set to 85 ° C. when performing the surface treatment of the substrate.
And different.

In other respects, samples (sample ratio 7-2), (sample ratio 7-5) and photovoltaic elements (ratio 7-2) were manufactured under the same conditions as in Example 7.

(Comparative Example 7-3) This example is different from Example 7 in that the surface treatment of the substrate was performed with an acid for 100 minutes.

The other conditions were the same as in Example 7, and samples (sample ratio 7-3), (sample ratio 7-6) and photovoltaic elements (ratio 7-3) were produced.

In the following, the substrates subjected to the surface treatment in the same manner as in Example 1, that is, (Sample 7-1), (Sample ratio 7-1), (Sample ratio 7-2), (Sample ratio 7
The results of the evaluation of (-3) will be described. Observe the surface shape of each, determine the difference in Rmax (Rmax (difference)) from the crystal grain size and the surface roughness of the substrate (maximum peak-to-peak value, hereinafter "Rmax"), and examine the schematic shape of the cross section of the substrate. Was.

The results are shown in Table 26.

[0316]

[Table 26] In the same manner as in Example 1 (Sample 7-2), as shown in Table 26, the surface of each crystal grain is divided into an uneven portion and a flat portion, and Rmax of the uneven portion and the flat portion is determined.
In contrast, in (sample ratio 7-1), the crystal grains were entirely flat and there was no difference in Rmax, and in (sample ratio 7-2) and (sample ratio 7-3), It has a pyramid-shaped uneven structure, and Rmax has no difference.

Also, the substrates prepared up to the transparent conductive layer in the same manner as in Example 1, ie, (Sample 7-2), (Sample ratio 7-4), (Sample ratio 7-5), (Sample ratio 7-7)
For -6), the surface shape was observed and Zn
The O crystal grain size was checked, and the total reflectance and diffuse reflectance were determined using a spectrophotometer equipped with an integrating sphere.

The results are shown in Table 27.

[0319]

[Table 27] In the same manner as in Example 1 (Sample 7-2), as shown in Table 27, the crystal grain size of ZnO forming the transparent conductive layer was large,
While both total reflectance / diffuse reflectance are excellent, (sample ratio 7-4) has a small crystal grain size and a low diffuse reflectance,
In (sample ratio 7-5) and (sample ratio 7-6), both the total reflectance and the irregular reflectance were very low.

In the following, similarly to Example 5, the above-described Example 7, Comparative Example 7-1, Comparative Example 7-2, and Comparative Example 7-
The results of evaluating the photovoltaic elements manufactured in No. 3, that is, (real-7), (ratio 7-1), (ratio 7-2) and (ratio 7-3) will be described. First, each of the five sub-cells was manufactured, and then divided into 25 sub-cells.
The shunt resistance was measured with a reverse bias voltage of 1.0 V applied. The reference value of the shunt resistor is 4 × 10 ⁴ Ωcm ²
Then, the yield was checked. Further, in the same manner as in Example 1, an adhesion test, measurement of initial photoelectric conversion efficiency (photovoltaic power / incident light power), photodegradation, high-temperature high-humidity reverse bias (HHRB) degradation, and temperature-humidity degradation were performed.

[0321] The results are shown in Table 28.

[0322]

[Table 28] As a result of the measurement, (ratio 7-1) was lower in yield and adhesion than (actual-7). Although the photoelectric conversion conversion efficiencies after each deterioration test are also inferior, these differences are mainly due to a decrease in FF due to a decrease in series resistance due to adhesion. In (Comparative 7-2) and (Comparative 7-3), the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after each deterioration were all lower values than (Exact-7). Regarding the initial photoelectric conversion efficiency, the short-circuit current (J
sc) decreased, and the photoelectric conversion efficiency after each deterioration was mainly due to a decrease in open circuit voltage (Voc).

As described above, the photovoltaic device of the present invention (actual
7) are conventional photovoltaic elements (ratio 7-1), (ratio 7-
2) It was found to have characteristics superior to (Comparative 7-3).

Example 8 In this example, the relationship between the polycrystalline average grain size of the polycrystalline substrate and Rmax (difference) was examined. Similarly to the first embodiment, the surface of the substrate is etched using an acid, and SUS430-BA and SUS430 are used as substrate materials.
Photovoltaic devices having the configuration shown in FIG. 1 were manufactured using SUS430-2B, SUS430-2D, and SUS304 mirror-finished plates.

In the same manner as in Example 1, a SUS
The surface of the substrate was etched using the acid shown in FIG.
A part of the substrate subjected to the etching treatment was evaluated (Samples 8-1 to 81), and thereafter, an AgAl alloy reflective layer was formed under the conditions shown in Table 29 in the same manner as in Example 1. AgAl
After forming the alloy reflective layer, a ZnO transparent electrode layer was formed under the conditions shown in Table 29, and a part of the substrate was left for evaluation (Samples 8-1 to 81-81). Then, a pin type semiconductor layer, an In ₂ O ₃ transparent electrode, and a current collecting electrode were formed in the same manner as in Example 1 to produce a photovoltaic element (Examples 1 to 81).

[0326]

[Table 29] For the substrate subjected to the surface treatment in the same manner as in Example 1, that is, (Samples 8-1 to 81), the surface shape was observed, and the difference (Rmax) between the crystal grain size and the substrate surface roughness (Rmax) was measured.
(Difference)) and the schematic shape of the cross section of the substrate.

The results are shown in Table 30.

[0328]

[Table 30] From Table 30, it was found that the crystal grain size was 0.05 μm to 3200 μm, and the difference in surface roughness (Rmax (difference)) was in the range of 0 to 8.2 μm.

For the substrates (samples 8-1 to 81-81) fabricated up to the transparent conductive layer in the same manner as in Example 1, the surface shape was observed, the ZnO crystal grain size was checked, and the total reflectance and diffuse reflectance were determined. . As a result, the crystal grain size becomes Rmax
It was found that when the (difference) was 0.01 μm or more, the cells grew to a good size. On the other hand, the total reflectance and the irregular reflectance are R
If max (difference) is smaller than 0.01 μm, the diffuse reflectance is low, and if max (difference) is larger than 1.50 μm, the total reflectance is reduced.

Suitable etching conditions (Sample 8-2)
1 to 24, 30 to 33, 39 to 42, and 48 to 51), the crystal grain size of ZnO is large, and the total reflectance / diffuse reflectance;
It turned out that both were excellent.

In the same manner as in Example 1, the photovoltaic element (actual 8-
1 to 81), each was manufactured in 5 pieces, and further divided into 25 subcells, the yield was examined, the adhesion test was performed, and the high-temperature high-humidity reverse bias (HHRB) deterioration,
Each test of temperature and humidity deterioration was performed.

The results are shown in Tables 31 to 34.

[0333]

[Table 31]

[0334]

[Table 32]

[0335]

[Table 33]

[0336]

[Table 34] As a result of the measurement, (actual 8-21 to 24, 30 to 33, 39 to
42, 48 to 51), the others had low yield and low adhesion. Each crystal grain size is 0.1
μm or Rmax (difference) 0.01 μm
The smaller ones are also inferior in the photoelectric conversion efficiency after the deterioration test, but these are mainly due to the lowering of the FF due to the lowering of the series resistance due to the adhesion. Further, those having a crystal grain size larger than 3000 μm or Rma
When x (group) was larger than 1.50 μm, the photoelectric conversion efficiencies after each deterioration were all low values, but this was mainly due to the decrease in open circuit voltage (Voc).

As described above, the photovoltaic device in which the polycrystalline substrate of the present invention has an average polycrystalline particle size of 0.1 μm to 2 mm and an Rmax (difference) of 0.01 μm to 1.5 μm is excellent. It has been found to have properties.

(Embodiment 9) In this embodiment, a step of a polycrystalline substrate was examined. In the same manner as in Example 8, the surface of the substrate was etched using an acid, and SUS43 was used as the substrate material.
0-BA, SUS430-2B, SUS430-2D,
A photovoltaic element having the configuration shown in FIG. 1 using a SUS304 mirror-finished plate was manufactured.

[0339] In the same manner as in Example 8, on a SUS substrate, Table 35
The surface of the substrate was etched using the acid shown in FIG.
A part of the substrate subjected to the etching treatment was evaluated, and then, as in Example 8, an Al reflective layer was formed under the conditions shown in Table 35. After forming the Al reflective layer, the ZnO transparent electrode layer was formed under the conditions shown in Table 35, and then the pin semiconductor layer, the In ₂ O ₃ transparent electrode, Electrodes were formed to produce a photovoltaic element.

[0340]

[Table 35] The surface shape of the substrate subjected to the surface treatment in the same manner as in Example 8 was observed, and the crystal grain size was 6.0 μm and Rmax
After selecting a substrate having a (difference) of 0.2 μm, the distribution of Rmax was examined.

As a result, Rmax was 0.005 to 3.5 μm.
m.

These substrates were fabricated up to the photovoltaic element in the same manner as in Example 8, the yield was examined, and the adhesion test, the high-temperature high-humidity reverse bias (HHRB) deterioration, and the temperature-humidity deterioration tests were performed. Was.

The results are shown in Tables 36 to 39.

[0344]

[Table 36]

[0345]

[Table 37]

[0346]

[Table 38]

[0347]

[Table 39] As a result of the measurement, those having an Rmax of 0.01 to 2.00 μm showed good results for all the tests,
When the value was 0.01 μm or less, the yield and the photoelectric conversion efficiency after the adhesion test were low. These are mainly caused by a decrease in FF due to a decrease in series resistance due to adhesion. If Rmax is greater than 2.00 μm,
Although the yield and adhesion are not so bad values, the photoelectric conversion efficiency after other deterioration tests is significantly inferior. These were mainly due to a decrease in open circuit voltage (Voc).

As described above, it has been found that the photovoltaic element of the present invention in which the step of the polycrystalline substrate is 0.01 μm to 2 μm has excellent characteristics.

[0349]

According to the first aspect of the present invention, in a photovoltaic device in which a polycrystalline material is used for a substrate and a non-single-crystal semiconductor is formed thereon, the polycrystalline material is exposed on the surface of the polycrystalline substrate. There is a difference in the flatness of the surface of the individual crystal grains of the polycrystal, and the following effects can be obtained by using a substrate in which the polycrystal grains having the uneven surface and the polycrystal grains having the flat surface are mixed. There is.

First, the adhesion between the thin film laminated on the polycrystalline substrate and the polycrystalline substrate is improved as compared with the case where a conventional polycrystalline substrate having a flat surface is used, In the power device manufacturing process, the thin film and the polycrystalline substrate are not separated from each other, so that the controllability and the degree of freedom of the manufacturing process are improved, and the manufacturing yield of the photovoltaic device is improved. In addition, as a result of accelerated weather resistance tests such as a high-temperature and high-humidity cycle test and a salt water test, weather resistance was improved. further,
As a result of mechanical strength tests such as a scratch test and a bending test, the durability was improved. In addition, due to irregularities on the surface of the polycrystalline substrate, irregular reflection on the back surface of the photovoltaic element increases, and long-wavelength light that could not be absorbed by the semiconductor layer is scattered, thereby extending the optical path length in the semiconductor layer. The short-circuit current (Jsc) of the photovoltaic element increased, and the photoelectric conversion efficiency improved. Further, the series resistance of the photovoltaic element was reduced, the fill factor (FF) was improved, and the photoelectric conversion efficiency was improved.
In addition, the leakage current of the photovoltaic element was reduced and the production yield of the photovoltaic element was improved as compared with the case of using a conventional polycrystalline substrate having uniformly unevenness on the surface. Further, the open-circuit voltage (Voc) and the fill factor (FF) were improved while the short-circuit current (Jsc) of the photovoltaic element was maintained at a high value, and the photoelectric conversion efficiency was improved.

Further, when the thin film laminated on the polycrystalline substrate is also polycrystalline, the orientation of the thin film laminated on the polycrystalline substrate is improved, and the average grain size of the polycrystalline thin film is reduced. The variation in the polycrystalline grain size of the thin film was reduced. As a result, the series resistance of the photovoltaic element was reduced, and the fill factor (FF) was improved. At the same time, light scattering was further promoted, and the short-circuit current (Jsc) was increased.

According to the second aspect of the present invention, a back metal reflective layer is formed on a polycrystalline substrate having the features of the first aspect, a transparent conductive layer is formed thereon, and a The formation of the non-single-crystal semiconductor enhances the reflectivity of the back surface of the photovoltaic element, and the polycrystalline substrate having the characteristics of claim 1 enhances irregular reflection, thereby producing a semiconductor. The optical path length in the layer was extended, the light absorption was increased, the short-circuit current (Jsc) of the photovoltaic element was further increased, and the photoelectric conversion efficiency was further improved. In addition, by improving the adhesion between the back metal reflective layer and the polycrystalline substrate, the degree of freedom and controllability of the manufacturing process of the photovoltaic element is improved, and the production yield is improved, and the photovoltaic element is improved. The weather resistance and durability have improved. In addition, since the transparent conductive layer has an appropriate resistance value, the current flowing in the defect region of the semiconductor layer is reduced, and the shunt of the photovoltaic element is reduced, and the production yield is improved. further,
When the polycrystalline substrate has the features of claim 1, the orientation of the back metal reflective layer and the transparent conductive layer is improved, the average grain size of the polycrystal of the back metal reflective layer is increased, and the variation in the grain size is increased. Has become smaller. As a result, the series resistance of the photovoltaic element is reduced, the fill factor (FF) is improved, and at the same time, light scattering is further promoted, and the short-circuit current (J
sc) increased.

According to the invention of claim 3, the surface of the back metal reflective layer formed on the polycrystalline substrate also has a difference in flatness according to the polycrystalline grain boundaries of the substrate.
The adhesion between the back metal reflective layer and the transparent conductive layer is improved, the degree of freedom and controllability of the photovoltaic element manufacturing process is further improved, the production yield is further improved, the weather resistance of the photovoltaic element,
Durability has been further improved. In addition, the surface of the back metal reflective layer also has a difference in flatness according to the polycrystalline grain boundaries of the substrate, so that the orientation of the transparent conductive layer is further improved, and the average grain size of the polycrystalline transparent conductive layer is reduced. And the variation in particle size became smaller. As a result, the series resistance of the photovoltaic element decreases, and the fill factor (FF) improves,
Light scattering at the interface between the back metal reflective layer and the transparent conductive layer and the interface between the transparent conductive layer and the semiconductor layer was further promoted, and the short-circuit current (Jsc) was further increased.

According to the fourth aspect of the present invention, the surface of the transparent conductive layer formed on the back metal reflection layer also has a difference in flatness according to the polycrystalline grain boundaries of the substrate, so that a transparent conductive layer is formed. The adhesion between the layers and the semiconductor layer is improved, the flexibility and controllability of the manufacturing process of the photovoltaic device are further improved, the production yield is further improved, and the weather resistance and durability of the photovoltaic device are further improved. did. Also, the surface of the transparent conductive layer has a difference in flatness according to the polycrystalline grain boundaries of the substrate, so that light scattering at the interface between the transparent conductive layer and the semiconductor layer is promoted, and the short-circuit current (Jsc) is increased. Increased further.

According to the invention of claim 5, since the surface of the photovoltaic element also has a difference in flatness according to the polycrystalline grain boundary of the substrate, the light incident side of the photovoltaic element, especially the semiconductor layer Light scattering at the interface between the transparent electrode and the upper transparent electrode is promoted, and light is scattered on both the light incident side and the back side of the semiconductor layer. The absorption increased and the short circuit current (Jsc) further increased.

According to the invention of claim 6, a step is provided on the surface of the polycrystalline substrate along a polycrystalline grain boundary, or a protrusion or a depression is provided at a portion of the polycrystalline grain boundary. As a result, the adhesion between the thin film laminated on the polycrystalline substrate and the polycrystalline substrate is further improved, the degree of freedom and controllability of the photovoltaic element manufacturing process are further improved, and the production yield is improved. Further improved, the weather resistance of the photovoltaic element,
Durability has been further improved. In addition, due to steps or irregularities in the crystal grain boundaries on the surface of the polycrystalline substrate, irregular reflection on the back surface of the photovoltaic element increases, and long-wavelength light that could not be absorbed by the semiconductor layer is scattered into the semiconductor layer. , The short-circuit current (Jsc) of the photovoltaic element further increased, and the photoelectric conversion efficiency was further improved. Further, the orientation of the polycrystalline thin film laminated on the polycrystalline substrate was further improved, and the average grain size of the polycrystalline thin film was further increased. As a result, the series resistance of the photovoltaic element was reduced, and the fill factor (FF) was improved. At the same time, light scattering was further promoted, and the short-circuit current (Jsc) was increased.

According to the seventh aspect of the present invention, the main material of the polycrystalline substrate is a metal or an alloy, so that flatness is made different depending on polycrystalline grain boundaries.
In addition, it is easy to form steps along the polycrystalline grain boundaries or to form irregularities at the polycrystalline grain boundaries. In addition, flexibility is generated in the substrate, and the degree of freedom in processing in manufacturing the photovoltaic element is improved. In addition, since both the polycrystalline substrate and the back metal reflective layer are made of metal, the adhesion between the polycrystalline substrate and the back metal reflective layer is further improved, and the orientation of the back metal reflective layer is further improved. . Due to the improved adhesion, the processability of the substrate is further improved, and the flexibility and controllability of the manufacturing process are further improved.

According to the invention of claim 8, the main material of the back metal reflection layer includes gold, silver, copper, aluminum,
By using a material containing a metal having a high reflectance of visible to infrared light such as magnesium, the reflectance of the back surface of the photovoltaic element is further improved, and the light absorption of the semiconductor layer is increased,
The short-circuit current (Jsc) of the photovoltaic element was further improved.

Also, there is a difference in the flatness of the surfaces of the individual crystal grains of the polycrystal exposed on the surface of the polycrystalline substrate, and polycrystal grains having irregularities on the surface and polycrystal grains having a flat surface are different. By laminating the above-mentioned metal with high reflectivity on a mixed polycrystalline substrate, high diffuse reflection and high short-circuit current (Js
While maintaining c), the metal having a high reflectance described above hardly diffused into the semiconductor layer or caused migration, so that the yield of manufacturing photovoltaic devices was significantly improved. Further, the leak current of the photovoltaic element was reduced, and the open voltage (Voc) and the fill factor (FF) were improved.

Also, there is a difference in the surface flatness of each of the polycrystalline grains exposed on the surface of the polycrystalline substrate, and the polycrystalline grains having irregularities on the surface and the polycrystalline grains having a flat surface are different. By stacking aluminum on the mixed polycrystalline substrate, while scattering light on the back surface, the total reflectance of the aluminum surface including the case where the transparent conductive layer is stacked is not reduced, The light absorption of the semiconductor layer was improved by the high total reflectance of the aluminum surface, and the short-circuit current (Jsc) of the photovoltaic element was improved. In addition, the adhesion between the substrate and aluminum was improved, the flexibility and controllability of the manufacturing process were improved, the manufacturing yield was improved, and the weather resistance and durability of the photovoltaic element were improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a layer configuration of a photovoltaic device according to the present invention.

FIG. 2 is a schematic sectional view showing another example of the layer configuration of the photovoltaic device according to the present invention.

FIG. 3 is an example of an electron micrograph of a substrate of a photovoltaic device according to the present invention.

FIG. 4 is a schematic plan view showing a collecting electrode of the photovoltaic device according to the present invention.

FIG. 5 is a schematic cross-sectional view showing a sputtering apparatus suitable for producing a substrate of a photovoltaic device according to the present invention.

FIG. 6 is a schematic sectional view showing a deposition film forming apparatus suitable for producing a photovoltaic element according to the present invention.

FIG. 7 is a schematic cross-sectional view and a plan view showing a roll-to-roll type deposited film forming apparatus suitable for producing a photovoltaic element according to the present invention.

[Explanation of symbols]

101, 201 substrate, 102, 202 back metal reflective layer, 103, 203 transparent conductive layer, 104, 204, 207, 210 n-type semiconductor layer, 105, 205, 208, 211 i-type semiconductor layer, 106, 206, 209, 212 p-type semiconductor layer, 107, 213 transparent electrode, 108, 214 current collecting electrode, 501 processing chamber, 502 substrate, 503 heater, 504, 508 target, 506, 510 power supply, 507, 511 shutter, 512 pressure gauge, 513 conductance Valve, 514, 515 supply valve, 516, 517 mass flow controller, 600 deposition device, 601 load lock chamber, 602, 603, 604 transfer chamber, 605 unload chamber, 606, 607, 608, 609 gate valve, 610, 611, 612 units Heater, 613 a substrate transfer rail, 631～634,641～644,651～655,6
61 to 666, 671 to 674, 681 to 684 Stop valve, 636 to 639, 656 to 660, 676 to 679 Mass flow controller, 617, 618, 619 Deposition chamber, 620, 621 electrode, 622, 623, 624 RF power supply, 628 Bias electrode, 649 gas supply pipe, 650 shutter, 701-713 deposition chamber, 714 separation passage, 715 source gas inlet, 716 exhaust port, 717 RF electrode, 718 microwave applicator, 719 scavenging gas inlet, 720 bias electrode, 721 delivery Roll, 722, 724 Guide roller, 723 Take-up roll, 729 Delivery room, 730 Take-up room.

Claims (11)

[Claims] In a photovoltaic device in which a non-single-crystal semiconductor is formed on a substrate made of a polycrystalline material, the surface of each of the polycrystalline grains exposed on the surface of the substrate has a flat surface. A photovoltaic element, wherein a substrate is used in which a polycrystalline grain having a surface having irregularities is mixed with a polycrystalline grain having a flat surface. 2. A back metal reflective layer is formed on the substrate, a transparent conductive layer is formed on the back metal reflective layer, and a non-single-crystal semiconductor is formed on the transparent conductive layer. The photovoltaic device according to claim 1, wherein 3. The photovoltaic device according to claim 1, wherein the surface of the back metal reflection layer has a difference in flatness according to a polycrystalline grain boundary of the substrate. 4. The photovoltaic device according to claim 1, wherein the surface of the transparent conductive layer has a difference in flatness according to a polycrystalline grain boundary of the substrate. Power element. 5. The light according to claim 1, wherein the surface of the photovoltaic element has a difference in flatness according to a polycrystalline grain boundary of the substrate. Electromotive element. 6. The method according to claim 1, wherein a step is formed along a grain boundary of the polycrystal on the surface of the substrate, or a protrusion or a depression is formed on a grain boundary portion of the polycrystal. Item 2. The photovoltaic element according to Item 1. 7. The photovoltaic device according to claim 1, wherein a main material constituting the substrate is a metal or an alloy. 8. A material having a high reflectance from visible to infrared light, such as gold, silver, copper, aluminum, or magnesium, which is a main material constituting the back metal reflection layer. 8. The photovoltaic device according to any one of items 7 to 7. 9. The difference in surface flatness between individual crystal grains of the polycrystal exposed on the surface of the substrate is 0.01% as the difference in Rmax.
The photovoltaic device according to any one of claims 1 to 8, wherein the photovoltaic device has a thickness of from 1.5 µm to 1.5 µm. 10. The polycrystalline average grain size of the substrate is 0.1.
The photovoltaic device according to claim 1, wherein the photovoltaic device has a thickness of 1 μm to 2 mm. 11. A height or depth of a step along the grain boundary of the polycrystal, or a height or a depth of a bulge or a depression of a grain boundary portion of the polycrystal on the surface of the substrate, is 0.01 μm to 2 μm. The photovoltaic device according to any one of claims 1 to 10, wherein: